The numbers man Associate Professor Guido Menzio was booted off the aircraft and questioned by some mysterious agents who refused to be identified, after the female passenger sitting next to him said she felt ill.
He showed the 'agents' what he had been working on and the flight (with Prof. Menzio back on board) took off - but more than two hours late. Prof. Menzio (pencil confiscated) told the Washington Post "the pilot seemed embarrassed".
He wrote on Facebook 'the experience' was "unbelievable" but it made him laugh, he didn't say if his fellow passengers saw the joke...
The University of Pennsylvania associate professor boarded the Philadelphia-Syracuse flight on Thursday on his way to Ontario, where he was due to give a lecture.
Before the flight took off, the woman sitting next to him passed a note to a member of the cabin crew. She initially told them she was feeling unwell, but then voiced her suspicions about Mr Menzio's scribblings.
He wrote on his facebook page:
"It's a bit funny. It's a bit worrisome.
"The lady just looked at me, looked at my writing of mysterious formulae, and concluded I was up to no good.
"Because of that an entire flight was delayed."
He told Associated Press that the crew should have run additional checks before delaying take-off.
He said: "Not seeking additional information after reports of 'suspicious activity' is going to create a lot of problems, especially as xenophobic attitudes may be emerging."
American Airlines, whose regional partner Air Wisconsin was operating the flight in question, said the crew followed protocol to take care of an ill passenger and then to investigate her allegations.
It was established that they were not credible.
The woman was re-booked on a later flight. American Airlines are probably now advising passengers who wish to work out 'differential equations' to try playing hangman or do the London Times Crossword, just as frustrating.
Source: BBCNEWS, Washington Post, Reuters
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