As a reaction to an additional german trans in the baltic or any other placement of ground forces in Eastern Europe an addtional fighter would raise the russian airforce to 2 fig, 1 bmb.
Pro:
Trading countries with airforce assistance minimizes failure in your attack and losses on the enemy counterattack. One additional reusable attack unit is excellent to slow german progress at reasonable costs.
And should it all go wrong there is an additional 4 defending Moscow.
Con:
1 fig is less pieces than 4 inf or 3 art