Broken Airplanes
Read the preamble for MELs. The time limits imposed are MAXIMUM time periods...not ETRs (estimated time of repairs). The intent and spirit of the MEL system is to have the plane fixed ASAPractical...with a maximum time limit specified. This philosophy is explicitly stated in the MEL preamble.
Many airlines are government owned/controlled. So, the governments, themselves, can make any rule they want...and it's legal. There is no legal requirement to follow aircraft certification criteria. They make the rules...and it's legal when they come up with 'exceptions' and special cases.
However, not being an aviation lawyer, I can't speak of the legal ramifications through ICAO, international flying, etc., when an airline pulls this nonsense. (Feel free to substitute another eight-letter word, here.)
Most 'real airlines' are governed by state rules that require routine maintenance and repair. This means that the airlines must carry sufficient parts, have a Q/A department to oversee maintenance.
Then, you have Fumbuck Airways, the national airline of Slobokia...where the MEL system is abused to allowed for deferral of routine maintenance (brake on MEL due to wear, is a classic example), or the swopping of a broken part to another aircraft to get another ten days out of the system, or the swopping of a part within a particular aircraft (e.g. IRU 3 inopt...wait ten days...then exchange it with IRU 2...and get another ten days out of the system).
I've seen nonsense where the MEL requires that an aircraft cannot depart a station where repairs can be made. The particular station is the major maintenance base for the airline...and they claim repairs can't be made due to no parts in stock. Again, under the intent and spirit of the aircraft certification (and the associated MMEL system), the airline is 'expected' to have a parts department.
Then, there's the MMEL/MEL issue. Under ICAO and fundamental MEL/aircraft certification regulations, the MEL cannot be any less restrictive than the MMEL. But, at many fly-by-night outfits (government owned and controlled) you'll see otherwise. If you ever get the chance to compare, page by page, the manufacturer's MMEL to your airline's MEL, do it. It may be an enlightening find!
In theory, the aircraft commander is the final safety check point to filter out the nonsense from the safe and legal to go. Unfortunately, and there are legal precedents illustrating this, the commander can be disciplined, sued, sacked, beaten (no kidding!) for carrying out this duty.
PantLoad