From the History Commons Groups blog:

Entries have been added to the Complete 9/11 Timeline at History Commons, which, in particular, reveal new details about events from the day of September 11.

Several entries describe how a group of fighter jets from Otis Air National Guard Base in Massachusetts were taking part in a training mission when the terrorist attacks began. Although the pilots of these jets had seen two other fighters taking off from their base in response to the hijacked Flight 11, they were unaware of the reason for the scramble. They therefore continued with their training mission--described as a "mock war scenario"--over the Atlantic Ocean.

The fighters were recalled to Otis Air Base after the base started preparing all of its fighters for takeoff. At least one of the pilots involved in the training mission soon took off again. Along with another pilot, his first task was to intercept a military cargo plane over the Atlantic. The two fighters were subsequently sent to New York, where they helped patrol the airspace over the city. Before returning to their base, they were directed to inspect a supposedly suspicious aircraft that turned out to be just a tanker plane that had been providing them with fuel.

Military personnel were also concerned about a convoy of aircraft approaching America across the Atlantic, which repeatedly failed to respond to radio communications. But when fighters intercepted the convoy, they found it was just some military planes coming back from Europe.