HOUSTON— Passengers aboard a Continental Airlines flight bound for Houston Tuesday sprang into action to help a flight attendant having trouble with an unruly passenger. Twenty minutes after the plane departed Portland, pilots returned to the city where the FBI was waiting. Passengers said the unruly man was a problem from the beginning. After boarding Flight 1113, the man became upset because he was not seated next to his friend. Then after the flight took off, he ignored the “No Smoking” sign and tried to light an electronic cigarette. A flight attendant asked the passenger to turn off the cigarette,...