Most passenger airliners do NOT fly over 40k. The 747 can get up to 41 or 42 for regular flight sometimes. The 737 will generally not go above 39. Most airliners CAN fly slightly above 40, but not above 45. Most will not. There is a higher risk of engine starvation and flame out, along with a drop in power, efficiency and control response.

Concorde would fly up to 52k.

Some smaller jets can fly well above 40, including CRJs. Some private jets like the Gulfstream 400's can do up to 50k.

Some military planes, particularly faster ones, can go up to 60. I think the U2 was capable of mid 80k.