The cause of the deadly Ukraine International Airlines Boeing 737 jet crash remains a mystery, but one pilot and aviation analyst believes the timing of the accident is “very suspicious.”

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The flight burst into flames shortly after takeoff, killing all 176 on board early Wednesday just hours after Iran fired missiles at U.S. air bases in Iraq. Both black boxes were found, but many questions are being raised because Iran is refusing to hand them over to Boeing. The crew of a Ukrainian jetliner never made a radio call for help and were trying to turn back for the airport when their burning plane went down, an initial Iranian investigative report said Thursday. Ukraine, meanwhile, said it considered a missile strike as one of several possible theories for the crash, despite Iran's denials.

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The Ukraine International Airlines flight crashed just 6 miles from Tehran airport. Flight tracker data shows it climbed to about 8,000 feet before losing all contact.

Kyle Bailey told FOX Business’ Neil Cavuto that “everything” appeared to be “normal.”

“The plane climbed at a normal set rate. The speed appeared normal,” he said, adding that in crashes you’ll see altitude and airspeed fluctuations “like crazy.”

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Bailey also noted that the aircraft has the ability to “climb normally” with one engine and the pilot should have “had time to contact air traffic control” or “make some kind of distress call” before losing contact.

The U.S. State Department issued a statement on the black box saying, “The United States will continue to follow this incident closely and stands prepared to offer Ukraine all possible assistance. The United States calls for complete cooperation with any investigation into the cause of the crash.”

Iran is responsible for investigating the crash, according to international rules.

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Boeing says it is ready to assist “in any way needed.”

“This is a tragic event and our heartfelt thoughts are with the crew, passengers, and their families,” the airliner said in a statement. “We are in contact with our airline customers and stand by them in this difficult time. We are ready to assist in any way needed.”

The Associated Press contributed to this report.

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