Sometimes airlines can lease from another company whan an Aircraft is sitting on the ground for a while...
Qantas has leant its 747's on occasions during the long layover at LHR
Also is an Aircraft is out of service for scheduled MX
, it may be out for 24 hours, but the check over takes a man day 8 Hours.. therefore this can be re-called earlier..
I know bmi have done this with the A330 in MAN
a few years back.
Also various operators have aircraft sitting about between work scattered across europe.. and its bound to be true across the world.
Air Pullmantur have offered their 747's on occasions for replacement Tech aircraft on european flights.
Other times.. it's just late... 6 hours, 12 hours, 2 days whatever...
I famously remember in 2002 a 747 belonging to UA
was damaged in turbulance over New Zealand. The A/C landed at Auckland and the passengers went to hotel over night whilst a replacement was flown from SFO
Next morning they boarded and took off for the replacement to suffer engine problems and return to Auckland. The passengers overnighted a second night.
The third morning they took off in the now repaired first aircraft and arrived 2.5 days late in SFO
.. with a refund and free anywhere worldwide first class ticket for two.
So far in 2008 45 flights and Gold already. JFK, IAD, LGA, SIN, HKG, NRT, AKL, PPT, LAX still to book ! Home Airport LCY