Definition: In this task, a passage will be given and the goal is to identify an event from the passage. An event is defined as a single word representing something that happened, is happening, or may happen. An event can be factual or hypothetical, positive or negative, certain or uncertain. While most events are based on verbs, an event can also be based on a noun (ex. storm, snow, rainfall) or a copula verb (is, was, been, etc.). The event must not be a pronoun or an adjective. For noun events with multiple words, use the last word in the phrase as event.
Input: Passage: With a host of European countries concerned over possible implication in Washington's "war on terror", questions have been raised about 32 flights by US-registered aircraft in Swiss airspace between early 2003 and December this year. On November 27, the Swiss government demanded explanations from Washington about 27 overflights of its territory by US planes in 2003 and 2004.

explanations