As of the summer of 2007, 129 countries were parties to this treaty, including such large ones as the
United States of America,
India, and
Australia. However, Brazil, Russia, Indonesia, and China never joined, and Canada left the treaty in 1988.
[9] These large and strategically located non-IASTA-member states prefer to maintain tighter control over foreign airlines' overflight of their airspace, and negotiate transit agreements with other countries on a case-by-case basis.
[3]:23
According to the Wikipedia quote above, Canada left the treaty in 1988, but my question was really about whether the UK's overflight rights over the territory of the Russian Federation would be affected by our leaving the EU next year.