Mission Types:

SA: Strategic Attack. When you attack a city or an airfield.
TA: Tactical Attack. When you attack a enemy sector, sending tanks to capture it.
SUM: SUply Mission. When you do a suply on a friendly city/airfield.

Tasks:

BA : Bomber Attack. Group of bombers attacking city or airfields.
SUM: SUply Mission. Group of transport planes, doing suply mission task
BD: Bomber Defend. Group og defending bombers, attacking the incoming enemy tanks
EBA: Escort BA bombers
ESU: Escort SUply transports
EBD: Escort BD bombers
ET: Escort Tanks. When you attack a sector, planes doing air cover and intercept enemy BD
INT: INTercept. In general, intercept enemy Suply transports and enemy BA.