Alberta's top court has dismissed an appeal by the group opposed to the closure of Edmonton's City Centre Airport.

The Alberta Court of Appeal upheld a lower-court ruling which found the petition from Envision Edmonton was invalid as it was not filed in time.

The group collected 92,563 signatures in hopes of forcing the city to hold a plebiscite on the closure during the 2010 municipal election.

But the city clerk found that only 74,000 signatures were valid. She also found that the petition should have been filed by Sept. 7, 2009, 60 days after council's decision to approve the phased closure of the airport.