Another dry run?
From a story from the Washington Times, Scouting jetliners for new attacks, talks about the Jacobsen story, a Feb. 15 incident on American Airlines Flight 1732 from San Juan, Puerto Rico, to New York's John F. Kennedy Airport, and other incidents:

The pilot confirmed Mrs. Jacobsen's experience was "terribly alike" what flight attendants reported on the San Juan flight.     He said there is "widespread knowledge" among crew members these probes are taking place.     A Middle Eastern passenger attempted to videotape out the window as the plane taxied on takeoff and, when told by a flight attendant it was not permitted, "gave her a mean look and stopped taping," said a written report of the San Juan incident by a flight attendant.     The group of six men sat near one another, pretended to be strangers, but after careful observation from flight attendants, it was apparent "all six knew each other," the report said.     "They were very careful when we were in their area to seem separate and pretended to be sleeping, but when we were out of the twilight area, they were watching and communicating," the report said.     The men made several trips to the bathroom and congregated in that area, and were told at least twice by a flight attendant to return to their seats. The suspicious behavior was relayed to airline officials in midflight and additional background checks were conducted.     A second pilot said that, on one of his recent flights, an air marshal forced his way into the lavatory at the front of his plane after a man of Middle Eastern descent locked himself in for a long period.     The marshal found the mirror had been removed and the man was attempting to break through the wall. The cockpit was on the other side.
. . .  Recent incidents at the Minneapolis-St. Paul international airport have also alarmed flight crews. Earlier this month, a passenger from Syria was taken into custody while carrying anti-American materials and a note suggesting he intended to commit a public suicide.     A third pilot reported watching a man of Middle Eastern descent at the same airport using binoculars to get airplane tail numbers and writing the numbers in a notebook to correspond with flight numbers.     "It's a probe. They are probing us," said a second air marshal, who confirmed that Middle Eastern men try to flush out marshals by rushing the cockpit and stopping suddenly.

Was the Jacobsen incident a dry run?  As Michelle Malking put it, Better a false alarm than a flaming plane.