Link
Using the hidden city tactic is usually practical only for one-way trips, as the airlines will cancel the subsequent parts of the trip once a traveler has disembarked. Thus, round-trip itineraries need to be created by piecing two one-way flights together. This tactic also requires that the traveler have carry-on luggage only, as any checked baggage items will be unloaded only at the flight's ticketed final destination.[1] Exceptions to this requirement are when re-entering a country where luggage must be processed by customs agents or when changing airports or train travel is involved in the flight ticket. This allows for a traveler to reclaim their luggage but before rechecking for their final destination, the traveler can simply leave the airport.[2]
This strategy violated the airlines' fare rules. Someone doing it infrequently is unlikely to be pursued by the airline, but in the frequent flier community there are reports of passengers who do it repeatedly losing their frequent flier accounts, or at least being threatened with such a loss. Experienced fliers recommend that if doing it more than very occasionally, passengers not associate their frequent flier numbers with reservations using the hidden city trick. Passengers should only book hidden city tickets through the airlines' own website, to avoid generating a penalty to a travel agency.