For US business schools, you should not be worried that you have hit some imaginary cut-off age.
Although some MBA programs are known to look more towards younger candidates (For example Stanford and HBS), all business schools will consider someone your age.
As an older candidate, you will have to prove that it makes sense to return to school at this late stage of your career and that you are not merely encountering a mid-career crisis. You will also have to demonstrate that all of your time in the work world has been well spent. You should demonstrate progression, tangible contributions, and a high level of self-awareness, confidence, and maturity. A 37-year-old applicant who has spent 15 years in the same position without showing significant growth or progression will have a hard time being admitted to a top school. But this is not because they are 37 or because of the 15 years of experience. Rather, it is because they may have not demonstrated growth during that time.
I hope this was of help.
Conrad and the Stacy Blackman
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MBA blogger, US News and Author, The MBA Application Roadmap