The problem is that if you send a signal by, say, firing off a flare, you're supposed to aim the flare well over the heads of the folks in the lifeboat.

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Officials said earlier Thursday that one of the U.S. planes fired a flare to ward off the Iranian fighter, but later said no flare had been fired.

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During the service, a flare was set off at 1213 BST, the exact time of the launch a century on.

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