Re: Detaining pax on board - Legalities?
Speaking from a pax point of view I think a lot of the problem with this thread is that there are 2 separate questions which many are trying to give the same answer for.
The first question relates to the original post re Ryanair. To me, and I suspect to many on here who are aware of RYR's desire to minimise costs wherever possible they are tenuously using the legal argument to avoid anything that a) might cost them money (I am guessing that an airport would charge them a fee for pax that disembarked, but would not for those that remained on board), and b) might cost them time (having to disembark pax when all you want is a quick gas-and-go or to be in a position to take up a slot at seconds notice). Saying it is illegal usually makes for a shorter argument that saying that it is inconvenient or costly to the airline.
The second question relates to how long an airline can reasonably expect pax to remain on board due to either a diversion or extensive departure delay. This is really a piece of string question - depends on the circumstances. Northwest had a class action with several thousand passengers after up to 11 hours delays in Detroit in 1999 due to snow, where they weren't allowed to leave the aircraft. Unfortunately this was settled out of court, so doesn't give a precedent, but I had a little sympathy with Northwest, as it seemed that the volume of snow meant that they were stuck between a rock and a hard place. However in general I would have thought that if a delay has gone on for more than a couple of hours a crew would need to have pretty pressing reasons for insisting that pax remain on board - such as a reasonable expectation that departure is imminent, or dangerous weather conditions making disembarkation unwise.
Personally I find that although a business, it is sometimes unclear whether commercial air travel is a customer service or not. Some posters here seemingly from the sharp end give the impression (unwittingly I suspect) that it is not, and as such the paying customers should just shut up and do what they are told.