I can't imagine food being so "bad" that a) it could incapacitate people within an hour or so, yet b) not so bad that it wouldn't be incredibly obvious that it was inedible.
Had nothing to do with food, or fumes. NOBODY was in critical condition. And it only affected four people; a woman got on the plane already sick, threw up, and people around her felt nauseous....
http://www.washingtonpost.com/wp-dyn/articles/A53806-2004Jul16.html
"Four people became ill last night on an airliner headed for Baltimore-Washington International Airport, prompting a flurry of anxiety as initial reports suggested that the situation was considerably more severe..."
"..Of the four who reported symptoms after the Southwest Airlines jetliner from Houston landed, one woman was taken to a hospital, where her condition was described as non-life-threatening. The other three declined hospitalization..."
"...Authorities said it appeared that she had been ill before boarding the flight at William P. Hobby International Airport and had thrown up while en route..."
"...They also said it appeared that others around her who reported becoming lightheaded and nauseated may have experienced those symptoms as a response to the woman's illness..."
"...One started throwing up, and others sitting nearby" did so afterward in a "reactive response," said BWI spokeswoman Cheryl Stewart. An airline spokeswoman said the others may have suffered from "sympathy nausea..."