Flight 3597 had originally been scheduled to land on runway 14, the main landing runway at Zürich, a runway equipped with an Instrument Landing System (ILS) that provides vertical and lateral guidance to the runway. The CVR records Lutz and Löhrer discussing "the 14 approach" as well as Lutz's request that Löhrer call out the height when the plane reaches 100 feet above DA (Decision Altitude – The altitude at which an immediate decision to land or initiate a missed approach must be made). However, Flight 3597 was behind schedule and would not reach Zürich until after 22:00 CET. This delay forced Flight 3597 to change its landing plan. Zürich Air Traffic Control Tower, in order to comply with a new Swiss law designed to reduce airport noise from approaching aircraft over southern Germany in the late evening hours, must redirect all flights on final approach to switch from the ILS-equipped runway 14 to the less-accurate VHF Omnidirectional Range (VOR)/Distance Measuring Equipment (DME)-equipped runway 28. This runway change forced Captain Lutz to abandon his planned ILS approach and required First Officer Löhrer to consult the Jeppesen charts for runway 28. The charts included a new set of approach parameters, of which the higher MDA (Minimum Descent Altitude) was the most crucial piece of information.