Atlas does the same 17 work days a month. It can be all at once or broken up a bit. One of the reasons some ACMI trips run longer is they are don't operate every day. A Pac Rim trip may have six crews playing tag around the Pacific. One crew will fly a plane to Hawaii and go to the hotel. They hand the plane off to a crew that brought a plane out a couple days earlier and have been sitting in Honolulu. The second crew will fly down to Australia and pass the plane to a third crew who will take it to a fourth crew in China who will give it to a fifth crew in Alaska who bring it to the lower 48 and a sixth crew will start out to Hawaii again. With two or three planes in the circuit you can do that in two weeks. But if you have to bring crews back from Australia or China after a week on the road and ship their replacement crew out your costs go way up. Plus if the crews self position by flying the plane to the next you have a crew waiting. If you're shipping crews out and something happens to the passenger flight your plane could show up and not have an onward crew.