Leg muscle cramps  

Ur not alone!  I've had leg cramps lasts minute or two fully convinced a bone could be broken.  Really horrible.

Hydrate more, especially prior to sleep, and NOT coffee, tea or alcohol which are diuretics.

When sleeping make sure your feet are not turned and held sideways by heavy or restricted blankets over your feet which tensions/compresses muscles causing the build of lactic acid which triggers the cramps. 

I've also found a normal glass of something like Gator-Aide in the afternoon helps.  

Never had the cramps full blown when flying but felt it could happen.  

Hydration is the most important - according to my doctor/AME.

Ur probably in your 50s?