Both passengers and crew will be required to make a new attestation before boarding flights to the U.S., starting Nov. 3.

Even a layover in one country could prevent passengers from boarding a U.S.-bound flight.

United, American, Southwest and Delta described the requirement as unworkable.

U.S. and international airlines are urging the CDC to delay its Nov. 3 Ebola travel form requirement affecting all U.S.-bound passengers. An infectious disease expert shares insights.

Americans need a yellow fever shot and an advance visa for the Republic of Congo, and a US Ebola flight rule starts Tuesday, 3 November.