The fact that no attack occured gives the talking heads leeway to claim there was no "terrorist attack."
A terrorist is a person who attempts to bring about political change by "illegitimate" (i.e., non-state) violence.
Mass murder is only terrorism if it is an attack on a political entity, or is an attempt to scare a nation's population into something.
Unless someone says, "We're going to keep crash your planes until you do such-and-such", this isn't terrorism. There's no attempt to bring about political change involved, only murder, motive unknown.