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.
REC: RECon. When you do a recon on a enemy city/airfield.
SUG: SUply Ground mission. When you do a ground suply on a friendly city or airfield.
SUS: SUply Sea mission. When you do a sea suply on a friendly city
SL: Sea Landing mission. When you do a sea landing on a enemy city

Tasks:

BA : Bomber Attack. Group of bombers attacking city or airfields.
SUM: SUply Mission. Group of transport planes, doing suply mission task
R: Recon. Plane, doing recon mission task
BD: Bomber Defend. Group of defending bombers, attacking the incoming enemy tanks
BG: Bomber Ground. Group of defending bombers, attacking the enemy cargo vehicles, doing ground suply mission task
BS: Bomber Sea. Group of defending bombers/torpedos, attacking the enemy transport ships, doing sea suply mission task
BSL: Bomber Sea Landing. Group of defending bombers/torpedos, attacking the enemy landing ships, doing sea landing mission task
BET: Bomber Escort Tanks. When you attack a sector, planes attacking the enemy defend position
EBA: Escort BA bombers
ESU: Escort SUply transports
ER: Escort Recon plane
EBD: Escort BD bombers
EBG: Escort BG bombers
EBS: Escort BS bombers
ESL: Escort BSL bombers
ET: Escort Tanks. When you attack a sector, planes doing air cover and intercept enemy BD
EG: Escort Ground. When you ground suply on a friendly city or airfield, planes doing air cover and intercept enemy BG
ES: Escort Sea. When you sea suply on a friendly city, planes doing air cover and intercept enemy BS
EL: Escort Landing. When you sea landing on a enemy city, planes doing air cover and intercept enemy BSL
INT: INTercept. In general, intercept enemy Suply transports, enemy BA and enemy RE.
H: Hunters. Patrol enemy airfield for attackin landing plane. Only AI
RA: Recon AI. Additional recon. Only AI
BAA: Bomber Attack AI. Additional group of bombers attacking enemy airfields. Only AI