The aircraft is certified to -70c. The fuel got to -30c. Jet A has an FCOM limit of -36c. We were cruising at FL340
Depends on the type and the altitude. It isn’t always but a steady -70 Limit.
A 319s limit is -70 from about 32,000ft up.
A 320s limit gets colder with altitude. So at 34,000ft the 320 CEO lowest temp is about -67 depending on how you read the graph. It is only -70 from around 38,000ft.