Two Spanish Iberia airplanes stand on the tarmac at the Adolfo Suarez Madrid-Barajas airport in Madrid on Monday. Spanish air traffic controllers started a four-day partial strike that could affect some 5,300 flights.
J.J. Guillen/EPA /LANDOV
A screen shot provided by FlightAware shows airline traffic at 10:20 a.m. EDT Friday over the United States. A fire at a Chicago-area air traffic control facility grounded hundreds of flights.