While creation of the TCAs focused attention on VFR general aviation flying, those who fly IFR have, and continue to face, many direct costs for airspace access. For example, transponders and encoders were routinely required for IFR flying in large parts of the national airspace system, and for everybody above FL 180. DME or its equivalent is required to fly above 24,000 feet. Turbojets are required to have altitude alerting systems, and most must have collision avoidance equipment, and terrain awareness and warning systems. By next year anybody who wants to fly above FL 280 must have dual altimeter systems that have been specifically tested and certified to meet the standards of domestic reduced vertical separation minimums (DRVSM). And the pilots of those airplanes must be specifically trained and receive regular recurrent training on the use of the altitude-keeping equipment.