Originally Posted by
kdhurst380
You don't ever want to see an Airbus narrowbody going above 39,000ft regardless of circumstances, as that is it's service ceiling! The 737NG is capable of higher and it isn't unusual to see Ryanair/Jet2/TUI cruising at 40/41,000ft on longer bucket and spade routes.
service ceiling is just the point at which the max climb rate drops below 100ft/min. It’s not a limitation on max altitude per se.