What is the highest altitude commercial aircraft fly?

What is the highest altitude commercial aircraft generally fly? I know I have been in planes that flew between 25,000 and 35,000 ft. It seems that some international flights are on the higher end like 32,000 to 35,000 ft. Does anyone know if there are any regulations on what the highest altitudes allowed are? ... show more What is the highest altitude commercial aircraft generally fly? I know I have been in planes that flew between 25,000 and 35,000 ft. It seems that some international flights are on the higher end like 32,000 to 35,000 ft. Does anyone know if there are any regulations on what the highest altitudes allowed are? Are max altitudes any different for aircraft in Canada?
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