One is exhaust gas recirculation, which pumps cooled exhaust back into the engine air intake, lowering the combustion temperature and reducing NOx formation.

FORBES: Clearing the Air

The EPA engineers came up with a formula that automakers around the world have long been groping for--an engine that explodes fuel at such a relatively low temperature (below 2, 000 degrees Fahrenheit) that almost no noxious nitrogen oxides are produced.

FORBES: EPA, Inc.

The board also confirmed the right engine experienced a surge during a flight on January 13, and subsequent repairs included the replacement of a temperature probe.

CNN: Investigators find feather, other evidence on downed plane