What's up with planted knives on Delta flights?

Last week they found box cutter blades (like those used in the 9/11 attacks in 2001) on a Delta flight from Tokyo to Portland, Oregon.

And today they've found a knife on board a Delta flight from Pusan to Tokyo, which was to then go on to the United States.

olice are investigating a Delta Air Lines flight from South Korea to Japan after a small knife was found under passenger seats, an official said Tuesday.

The Delta flight with 86 passengers and eight crew members arrived at Narita, Japan from Pusan, South Korea. Afterward, cleaners found a folding knife with a blade about 2.8 inches (7 centimeters) long under seats, a Narita airport police official said.

It makes me wonder if Al Qaeda, which had used East Asia-originating flights as deadly trial runs for its more egregious terror acts, is up to something.