From: Near Portland, OR
There are essentially three different air groups on an Allied CVE.
1) A CVL air group. This only exists on the three large CVEs: CVE 26 Sangamon, CVE 28 Chenango, CVE 27 Suwanee. These were built on tanker hulls. They took part in the Operation Torch landings, then transferred to the Pacific. They lacked the speed and armor of a CVL, which is why they are classified as CVEs. This design was well liked, but tanker hulls were in high demand, so some other hull had to be found.
2) A standard CVE air group. These units will be designated VCF and VCT. In reality the 'T' and 'F' part of the designation wasn't actually there because the VC stood for composite air group. The WitP engine can't handle more than one type of aircraft in a unit, so they had to be divided. This was the typical combat group for a CVE in WW II in both the Pacific and Atlantic. In the Atlantic they were used as convoy escorts and in special hunter killer ASW TFs. Those ASW TFs were never used in the Pacific, so they are not available in game. In the Pacific, the primary duty was providing close support for landing TFs while they were unloading and to attack ground targets when there were no other threats. This freed up the fast carriers to respond to any naval forces sent to disrupt the landings.
3) A replenishment group. The squadrons will have a VR type, ie VRT, VRB, or VRF. These units are a fiction and so are the air groups. Most of the CVEs with these groups were used as aircraft ferries for at least part of the war. Some had their own CVE air group at some point. These air groups exist to allow the Allied player to keep running like the fast carriers did for as long as they did. Without them, trying to mount operations like the US actually did in 1944 and 1945 will probably fall over and die. It's a fiction to make the game work in the same fashion supply is vastly abstracted in game.
Types #1 and #2 can operate like normal CV air groups and do all the same operations. The VR units are too large to allow any kind of regular carrier ops.
Personally I take the VR units off the carriers and use them to train carrier pilots. By mid-1943 I have a steady supply of high quality USN pilots that keep the CV squadrons at high effectiveness. I then use the freed up decks with Marine squadrons to supply extra air cover for convoys into enemy air space, or I use them to ferry aircraft. I play against the AI though. Against a human player I might leave the VR squadrons on the carriers and use them for replenishment as they are intended.
WitP AE - Test team lead, programmer