Compression, also known as bridging substitutions, is a process whereby unusable arrival slots are shifted in time so the owner can again use that slot. Say, for example, an airline has 2 flights scheduled to arrive in EWR; flight 1 at 1300 and flight 2 at 1500. After a GDP is run, flight 1 is assigned a 1400 arrival slot and flight 2 receives a 1700 arrival slot. If flight 1 is canceled, flight 2 can't make use of the 1400 arrival slot because it occurs before its scheduled arrival time of 1500. Compression will allow the vacated slot to move down to where flight 2 can make use of it. There are some interesting mathematics associated with the compression. In general, users with a small presence at an arrival airport are the primary beneficiaries of the compression. There are also instances where an airline with a major presence at an airport can benefit from compression, but this usually requires a significant number of cancellations.

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Compression Demo Zip File (1.9MB) Posted 12/98. An interactive demonstration of the compression process by Desiree Asche (Metron, Inc.)
Compression and Excess Demand MS Word (51KB) Posted 7/28/98. Memo from Roger Beatty, Ken Howard and Rick Oiesen on compression resulting in excess demand. Gives an airline and command center perspective plus pros and cons of various solutions.	Perplexities of Compression MS Word (50KB) Posted 6/18/96. A memo from Rick Oiesen regarding issues concerning the compression algorithm. Questions posed at the end of Rick's memo contain answers from Mike Wambsganss (Metron, Inc.).