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DALLAS -- Southwest Airlines Co. says it has grounded 128 planes after failing to inspect backup hydraulic systems used to control the rudder if the main system fails.
The airline said Tuesday night that it had canceled 90 flights so far and it "is anticipating a very minimal impact to their operations" Wednesday. The grounding covers about one-fifth its fleet.
The move surprised passengers who reported that their flights were unexpectedly delayed at airports like Baltimore/Washington International, reports CBS News correspondent Jeff Pegues.
Southwest spokeswoman Brandy King said that, after discovering the missed inspections, the airline immediately notified federal safety regulators and began checking the planes.
A spokesman for the Federal Aviation Administration, Lynn Lunsford, said the FAA was working with Southwest and Boeing, which manufactured the planes, to evaluate a plan that would enable the airline to keep flying the planes until the inspections are completed over the next few days.
The carrier said in a statement that the agency had approved the plan, and it would extend for five days at most.
The missed inspections were first reported by The Wall Street Journal.
The newspaper cited the airline as saying the groundings "weren't the result of an airworthiness directive from the FAA."
King called the missed inspections inadvertent. She said the airline discovered that 128 of its Boeing 737-700 jets already had flown beyond the point at which the backup hydraulic systems were supposed to be inspected. She said safety was the airline's top priority, and it was working to fix the matter quickly.
This is the latest safety dust-up between Southwest and the FAA, says Pegues. Over the past few years, the airline has squared off with regulators over several high profile safety issues.
Just last summer, the FAA proposed a $12 million fine of Southwest for failing to comply with safety related repairs to 737s.
Dallas-based Southwest is the nation's fourth-biggest airline. It has 665 jets, all of which are some version of the Boeing 737, including nearly 450 of the 737-700. That model seats 137 or 143 passengers, depending on the layout.
A transportadora US Southwest Airlines, maior companhia aérea de baixo custo do mundo, anunciou aterramento 128 aviões na terça-feira porque os aviões não tinha sido devidamente inspecionados.

O porta-voz da empresa Brandy Rei explicou sistemas hidráulicos de backup de 128 da companhia Boeing 737-700 deveria ter sido inspeccionados mais cedo. Os sistemas de atraso para a inspeção de volta os principais sistemas de controle do leme.

King disse que o incidente é inadvertida e enfatizou o compromisso da companhia com a segurança. A companhia aérea decidiu aterrar os aviões envolvidos nas inspecções não atendidas e notificou as autoridades.

Desde o ano passado, a frota da Southwest Airlines teve cerca de 665 Boeing 737. A aviões incidente uninspected envolve cerca de vinte por cento da sua frota, e causou a companhia a cancelar cerca de 80 voos na terça-feira, com, possivelmente, outros 19 cancelamentos ontem.

Na sequência de ações da companhia aérea, a Administração Federal de Aviação governou aterramento dos aviões não é inspecções previstas obrigatórios são concluídas no prazo de cinco dias.