Story highlights "Here come our victims," the pilot wrote

Nok Air said the pilot is being investigated

Bangkok, Thailand (CNN) Thai budget carrier Nok Air has formally apologized to the country's former leader after one of its pilots wrote an "inappropriate" message about the flight she boarded.

The pilot in question, who has not been named, took a photo of former prime minister Yingluck Shinawatra together with her son and entourage while they were walking to board the aircraft.

He then posted it in a group chat with around 30 pilots and wrote: "Here come our victims."

Another pilot -- believed to be from another airline -- responded: "Perhaps CFIT should be arranged."

CFIT stands for "controlled flight into terrain" and is used to describe a scenario when a pilot in control of an aircraft crashes it.

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