Sadly, it is an arbitrary limit insofar that the pilots union opposes increasing it beyond 2 hours: http://www.gpo.gov/fdsys/pkg/FR-2008-03-07/pdf/E8-3949.pdf
Sadly, it is an arbitrary limit insofar that the pilots union opposes increasing it beyond 2 hours: http://www.gpo.gov/fdsys/pkg/FR-2008-03-07/pdf/E8-3949.pdf