As dptdexys says, you should definitely try without aircraft for a few games to keep your opponent guessing. Drawing up lists 'knowing' what the opponent is fielding is always problematic, but that said, air transports are always a risk, and it is still up to you to find ways of neutralizing the threat. Here goes - -
With only a single vampire or THawk, you are already limited to attacking an extreme flank (or later the rear) of an army where the AA umbrella is weaker. Essentially you will need to concentrate your efforts on the point to be attacked.
One of the first rules to remember is to put BMs on the enemy to suppress enemy AA (check up on AA suppression which is a little tricky). Artillery is good at reducing AA capability, quite apart from being especially usefull against 'horde' armies like the IG and 'Nids but you obviously have to wait until they have moved into range. Teleporting Termies/Swooping Hawks on a flank to shoot / support (or even assault) is another way of weakening or neutralising the AA umbrella, along with pre-emptive air-strikes or 'fly-by' long-range shooting attacks etc.
Keeping the aircraft off-table for a second turn or even a third turn strike is equally effective, but takes patience and nerves to prepare the ground in turn #1. (The Eldar Avatar and the Marine Supreme Commander are essential here to avoid 'mis-communication').
(Personally, I have always disliked the 'permanent' CAP in the 2008 updates, which makes turn #2 assaults more problematic - try dropping that rule.) Equally you could try starting with the transports empty to pick up their troops on turn #1 for a turn #2 assault. (If it survives, you will probabply have also got BMs on the enemy A/c, which in turn are then less likely to fly on turn #2). And I do hope the Eldar player has some Night wings to intercept (
NOT CAP) enemy fighters - - -
Finally the air strategy really depends on the strength of the "umbrella" at the point of the assault taking place. The Vampire can probably ignore up to 3x gargoyles and possibly a Hydra, as the odds of getting shot down are slim. However, unless the Eldar can attack within their own ground AA umbrella (one or even two formations of Falcons with Firestorms) there is something like a 55% chance that the Vampire will be toast to Tbolts on CAP.
The Marines THawk is much tougher as statistically it can survive up to 7 hits - the equivalent of TBolts on CAP and at least 4 Hydra (that is unless I am throwing the dice

) and again, having a Hunter in range will help disuade the TBolts.
Hope all that helps