New Delays Loom as F.A.A. Expands Airliner Review

The groundings at airlines like American, Alaska, Delta and Southwest resulted from a broader round of inspections, ordered by the F.A.A., to determine whether the airlines have complied with past directives to check airplane structures, wires, electronics and other components.

A second wave of audits began on March 30 and will continue through June 30. Laura J. Brown, a spokeswoman for the F.A.A., said it could not rule out further groundings. “We don’t know,” she said. “We find what we find.”

That will do little to reassure travelers, who face difficulties switching to other flights because planes are generally flying full on popular routes.