From June through August 1987, Premiere Airlines had the

1987 June - Aug - PA had best on time service.
1988 Jan - March - PA had worst on time service.

Something happened in this 87-88 time frame which caused delays of PA planes. This factor did not affect any other airline.
An explanation of this will tell us about something specific that PA experienced that others did not.

(A) Although Premiere Airlines only revoked its policy of routinely holding flights for late passengers in the fall of 1987, the other nine airlines never had that policy.

Something that sets PA apart. Ok. Let's see. PA had a policy of holding flights for late passengers. Later it revoked that policy so it stopped holding flights for late passengers. This should have IMPROVED PA's on time arrival, not deteriorated it. Hence this is not an explanation to the facts.

(B) Premiere Airlines reduced its business by 10 percent when it raised its rates in the fall of 1987 to compensate for rising gasoline costs.

How less business can lead to late arrivals, we cannot say.

(C) Premiere Airlines bought five new planes in the fall of 1987 that proved to have fewer mechanical problems than the ones they replaced.

They bought better planes. This should have improved their on time arrival (fewer problems). Not the explanation.

(D) Premiere Airlines serves New England, which has heavy winter snowfalls, whereas the other airlines do most of their business in warmer regions of the country.

Correct. If PA serves area of heavy winter snowfalls while others do not, this could explain the disruption in their schedule. Heavy snowfalls will cause delays and cancellations.

(E) Although all 10 airlines strive to keep their flights on schedule, overcrowded airports increased flight delays for all 10 airlines in January 1988 as compared with June 1987.
Something that affected everyone. Irrelevant.

Answer (D)
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Here are my notes:

A - contradicts
B - irrelevant
C - contradicts
D - explains halfway
E - doesn't distinguish from other 9

So, clearly the answer is D. After I got through choice D, I was expecting E to have an explanation that's a little more complete than D, which is something you see often in 700+ level questions. Taking shorthand notes on the relative quality of each option is an easy way to break down these problems. In those cases where there is no clear cut winner, you've quickly and effectively eliminated the options that you don't need to consider. This allows you to confidently review the 2 or maybe 3 options with any merit.

On longer passages, I also would have taken shorthand notes on the passage itself. For instance:
- 6-8/87 = best ontime service
- 1-3/88 = worst ontime service
- no change in other 9 carriers during that time
- Goal: find the cause for change in service

I picked A as well because it says Premier airlines revoked its policy of waiting for passengers in the fall of 1987. ---> more wait times beginning January.

On the negative control. None of the other airlines had this policy ever ---> they did not revoke anything and hence remained unaltered in their relative rankings.

"I don't understand how one could take the winter option. Do we just assume that the winter in New England is in December. WE would be assuming based on our prior knowledge that NEngland has winter in December. Isn't that dangerous?"

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Note:
I wrote the piece within quotes first, then realized even option A talks about "fall", I had assumed fall was SEpt - Nov, the NEngland reasoning I had falls off.

I do not have the official explanation for this. However, I found a page that has the following explanation:-

Stimulus: Among a group of 10 airlines, one airline experienced the best on-time service in the summer months of one year and the worst on-time service in the winter months of the next year. The ranking of the other nine airlines remained the same during this entire time.

Question: What point explains the change in on-time performance for one airline but not the others? The two time periods are identified as June—August and January—March. What distinguishes these two periods?

It is clear that two seasons are represented and, depending on the routes the airlines cover, two widely varying weather patterns. If Premiere Airlines is the only one of the 10 airlines that flies to parts of the country where heavy winter snowfalls frequently delay flights, then the seasonal change in the weather explains the change in its on-time performance while that of the other airlines remains the same.

A If the airline no longer delayed flights to accommodate its late passengers, the on-time performance would improve rather than decline, and this would contradict the explanation.
B The airline’s loss of business is unrelated to its on-time performance.
C Planes with fewer mechanical problems should have helped on-time performance, not hurt it.
D Correct. This statement properly identifies the factor that supports the explanation for the airline’s declining on-time performance: the regional weather-related delays specific to the routes it serves.
E The rankings are relative, so factors explaining delays for all 10 airlines do not explain why one airline went from best to worst while the other nine stayed the same.

From June through August 1987, Premiere Airlines had the best on-time service of 10 United States airlines. From January through March 1988, Premiere Airlines had the worst on-time service of the 10 airlines. The on-time performance ranking of the other nine airlines relative to each other remained unchanged.

Premise: June-August 1987 = PA best on-time service
Premise: January-March 1988 = PA worst on-time service
Premise: Other nine companies remained unchanged = This is important because it means that PA is to blame for its service. This makes the argument air-tight.

Which of the following, if true, would most contribute to an explanation of the facts above?

(A) Although Premiere Airlines only revoked its policy of routinely holding flights for late passengers in the fall of 1987, the other nine airlines never had that policy. - We need to break this down. It says that PA revoked its policy of routinely holding flights for late passengers in the fall of 1987. If this were true then the PA's on-time service should IMPROVE. This is a trap answer choice because it uses rather deep language.
(B) Premiere Airlines reduced its business by 10 percent when it raised its rates in the fall of 1987 to compensate for rising gasoline costs. - Out of scope
(C) Premiere Airlines bought five new planes in the fall of 1987 that proved to have fewer mechanical problems than the ones they replaced. - Out of scope
(D) Premiere Airlines serves New England, which has heavy winter snowfalls, whereas the other airlines do most of their business in warmer regions of the country. - Let's analyze this. Heave winter snowfalls delay the service time of PA. This is a possible (but for the sake of strategy let's just hold this) answer.
(E) Although all 10 airlines strive to keep their flights on schedule, overcrowded airports increased flight delays for all 10 airlines in January 1988 as compared with June 1987. - Doesn't make sense.

Which of the following, if true, would most contribute to an explanation of the facts above?

(A) Although Premiere Airlines only revoked its policy of routinely holding flights for late passengers in the fall of 1987, the other nine airlines never had that policy. INCORRECT, WEAKENER answer choice as if Premiere Airlines is not holding late passengers then its on boarding service time must improve

(B) Premiere Airlines reduced its business by 10 percent when it raised its rates in the fall of 1987 to compensate for rising gasoline costs.
OUT OF SCOPE ANSWER CHOICE
(C) Premiere Airlines bought five new planes in the fall of 1987 that proved to have fewer mechanical problems than the ones they replaced.- INCORRECT, WEAKENER instead the service time must improve of Premiere Airlines by this

(D) Premiere Airlines serves New England, which has heavy winter snowfalls, whereas the other airlines do most of their business in warmer regions of the country. CORRECT in line with pre thinking as serving New England which has heavy winter snowfalls delays the servicing time of Premiere Airlines as compared to other 9 airlines

(E) Although all 10 airlines strive to keep their flights on schedule, overcrowded airports increased flight delays for all 10 airlines in January 1988 as compared with June 1987. Incorrect as does not explains the reason why Premiere Airlines is the best during June-Aug and worst during Jan - March as compared to other 9 airlines

Which type of question is this
Strengthening or assumption?

This is a Resolve paradox question. Check more questions here: https://gmatclub.com/forum/search.php?s ... tag_id=123

Theory on Resolve paradox questions:
https://gmatclub.com/forum/concept-arti ... 63056.html
https://magoosh.com/gmat/gmat-cr-paradox-questions/
https://www.bloomberg.com/news/articles ... ng-paradox

Hope it helps.
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Unable to understand the question!

Picked up A

We need to figure out why Premier Airlines' on time performance became worse than that of the other airlines.

(A) says that Premier STOPPED waiting for late passengers. Ceasing to hold flights for late passengers should have made Premier's on time performance better, not worse.

(D), on the other hand, provides a reason why Premier's performance would have become worse than that of the other airlines during the winter months from January through March, heavy snow, which the other airlines don't have to deal with.

To get CR questions correct, we have to be careful to fully analyze what each choice is saying, rather than go with vibe or choose choice because it seems on topic.

Choice (A) is closely related to on time performance, but if we carefully analyze it, we see that it has the wrong effect. Choice (D), which mentions snow, may seem off topic, but turns out to be the correct answer.
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KarishmaB
One doubt here.

While choosing out option D, we are assuming "Heavy snowfalls will cause delays and cancellations. ", correct?
Does the GMAT expect us to know these facts? While solving Resolve a Paradox questions, is it viable to make such an assumption on the answer choices presented?

Yes, you are required to make these connections. Critical reasoning is based on real world situations and you are expected to make reasonable deductions. We know that bad weather conditions affect flights.
Deductive logic is the branch of logic that spells it all out exactly but it doesn't have a lot of relevance in the real world.
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The facts presented indicate that Premiere Airlines had the best on-time service among 10 airlines from June to August 1987 but had the worst on-time service from January to March 1988. The on-time performance of the other nine airlines remained unchanged. To explain these facts, we need to identify an option that provides a plausible explanation. Let's evaluate each option:

A. The fact that Premiere Airlines revoked its policy of routinely holding flights for late passengers in the fall of 1987, while the other nine airlines never had that policy, does not directly contribute to an explanation of the observed change in on-time service. This option does not explain why Premiere Airlines went from the best to the worst on-time performance.

B. If Premiere Airlines reduced its business by 10 percent when it raised its rates in the fall of 1987 to compensate for rising gasoline costs, it suggests a potential decline in resources or capacity. However, it does not directly explain why Premiere Airlines went from the best to the worst on-time performance.

C. If Premiere Airlines bought new planes in the fall of 1987 that had fewer mechanical problems than the ones they replaced, it could contribute to improved on-time performance during that period. However, it does not explain why Premiere Airlines later had the worst on-time service. This option does not provide a comprehensive explanation of the observed change in performance.

D. The fact that Premiere Airlines serves New England, which experiences heavy winter snowfalls, while the other airlines operate in warmer regions, suggests a possible explanation. Adverse weather conditions during the winter months could have affected Premiere Airlines' on-time performance, leading to a decline in their ranking. This option provides a plausible explanation for the observed change in performance.

E. The fact that overcrowded airports increased flight delays for all 10 airlines in January 1988, compared to June 1987, does not directly explain why Premiere Airlines went from the best to the worst on-time performance. This option suggests a general trend affecting all airlines, rather than a specific factor impacting Premiere Airlines disproportionately.

Based on the analysis, option D, "Premiere Airlines serves New England, which has heavy winter snowfalls, whereas the other airlines do most of their business in warmer regions of the country," most significantly contributes to an explanation of the facts presented. The adverse weather conditions in New England during the winter months could explain the decline in Premiere Airlines' on-time service and its change in ranking compared to the other airlines.