Too cold for the airframe structure ?
Sgnr
Interesting statement you are posting regarding the structural flexibility of airframe structures at low temperatures.
Looking at the environmental envelope of state of the art regional jets (e.g. the Embraer 145), narrow-bodies (A320-series) and wide-bodies (B747-400) shows a different picture. Since all of those airplanes are using the same selection of aluminum alloys for their primary structural components (spars, ribs, frames, stringers and skins), their low temperature margin is quite different: E145, -65°C up to FL370; A320, -70°C up to FL398 and last but not least, B747-400, -80°C up to FL451.
For example, spars and ribs of the 320-series are manufactured out of aluminum/zinc alloys (type 7010 and 7050), top skin panels of the main wing out of 7050 and the bottom skin panels out of aluminum/copper alloy 2024. They show excellent fatique strength over a broad temperature range even at low temperatures mentioned above.
Aluminum alloys are materials of choice even for cryogenic structural applications.
The structural components made out of the aluminum alloys chosen in all three aircraft are NOT the limiting factor for the environmental envelope.
Environmental envelopes are defined and tested during the FAR/JAR25 certification process according FAR/JAR 25.1527