Britannia and MyTravel have operated on the Hajj for a number of years now, predominantly out of Indonesia. The contracts are awarded by the Indonesian Ministry of Religion and operators have to meet fairly strict guidlines, age of aircraft for one. The contracts are damp lease, UK aircraft and flight deck, Garuda cabin crew. The aircraft get the Garuda stickers on the tail and side and operate under Garuda Hajj flight numbers, although they retain the G- reg. The overall operation is run by Garuda ops with small teams from the relevant airline in theatre as go-betweens and sorting out issues with their own crews. The engineering will generally be done by the airlines own detached engineers.
The operation itself is generally a good revenue earner, however the costs are also fairly high. Hotac for crew and ground staff, allowances, positioning costs, etc. The operation may or may not make a profit but at the end of the day it is better to have the aircraft on a 3 months contract than have them sitting on the ground in the UK trying to pick up ad-hoc work.