The chief foreign affairs correspondent of The Wall Street Journal was fired on Wednesday after evidence surfaced that he had become entangled in the business dealings of an Iranian-born aviation titan who was one of his key sources.

The correspondent, Jay Solomon, was a highly regarded veteran of The Journal and Washington diplomatic circles, and his dismissal came as a shock to the paper’s newsroom.

Shortly after the firing was announced, The Associated Press published a report detailing Mr. Solomon’s communications with Farhad Azima, an Iranian-born businessman, about a venture that at times involved aerial espionage in Iran and the sale of defense equipment to the United Arab Emirates.

It was unclear if Mr. Solomon ever formally entered into a commercial arrangement or received compensation tied to Mr. Azima, according to The A.P.