Story highlights The FAA says registration for Donald Trump's corporate jet has expired in January

The Trump campaign appears to have violated the FAA regulations by flying it to campaign events

(CNN) One of the planes in Donald Trump's fleet shouldn't be in the sky, according to the Federal Aviation Administration.

The FAA says registration for the Republican presidential front-runner's Cessna Citation corporate jet expired January 31. Based on sightings from CNN's political team embedded with the Trump campaign, the Trump plane appears to have violated the FAA regulations by flying it to campaign events after its registration had expired.

The FAA requires all aircraft be registered before they're flown.

"The aircraft registration of N725DT expired on January 31, 2016 and has not been renewed," FAA spokeswoman Laura Brown said in an email to CNN.

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