OK, Gromit, if "hostages" displeases you perhaps you'd prefer "FALSE IMPRISONMENT:"
false imprisonment:n. depriving someone of freedom of movement by holding a person in a confined space or by physical restraint including being locked in a car, driven about without opportunity to get out, being tied to a chair or locked in a closet. It may be the follow-up to a false arrest (holding someone in the office of a department store, for example), but more often it resembles a kidnapping with no belief or claim of a legal right to hold the person. Therefore, false imprisonment is often a crime and if proved is almost always the basis of a lawsuit for damages.
See:
http://dictionary.law.com/Default.aspx?selected=728
In any action where false imprisonment is the basis of the claim the airline will, obviously, throw-up SOME kind of "...claim of a...right to hold..." However, the specific circumstances of a given (tarmac) incident will probably govern how much credit, if any, the Court would give to the airline's "...claim..."
The first judgment, favoring a plaintiff, which is upheld by the US Supreme Court, would, doubtless, see an almost overnight change in the airlines' procedures relating to tarmac strandings.
The decision of the airlines to totally ban smoking was, significantly, affected by a successful action relating to the in-flight death of a passenger resulting from the inhalation of secondary cigarette smoke during a flight to the USA. In
OLYMPIC AIRWAYS V. HUSAIN (US Supreme Court, 2004) the Court affirmed a judgment partly arising from the neglegent act of a flight attendant. The decedant asked to be re-seated. Olympic alleged there were no vacant seats available. The Court appeared to hold that the flight attendant, not the decedant as Olympic had argued, was responsible for finding someone to switch seats with the decedant. In addition, the Court held Olympic was responsible for the death as a result of its decision to allow smoking on the flight. Olympic terminated service to the USA when it became apparent they might be forced to pay on the judgment. The Supreme Court's decision was rendered in 2004, while the death occured around December of 1997.
The point of this post is to suggest to aggrevied airline consumers that accepting worthless free flight vouchers is not always one's only option. Legal action, in some instances, is an option and is something the airlines will be far more responsive to than a complaint letter. To the "Airline Sympathizers," and "Employees" that have a problem with this I could really care less.