Never heard of a variation level 1, but in crewing and rostering a variation is an arrangement with the CAA to make a special amendment to the company's Flight Time Limitations.
For example an airline operating a night mail service might ask for a variation to allow its crews to operate for 5 consecutive nights, instead of the 3 consecutive nights normally allowed under CAP371.
To obtain the variation the airline will have to guarantee certain arrangements for crew benefit, such as extra days off prior to the commencement of the week's flying and additional rest afterwards as well. There will also normally be limits on how many hours the crew can operate for, which will be less than those under CAP371.
[This message has been edited by opsbod (edited 24 August 1999).]