As well as ICAO, the United Nations Treaty Collection can be a useful source for information about international air services arrangements that have treaty status. The web site has recently be revamped.
However, as with the ICAO treaty collection (DAGMAR), the UN collection is by no means comprehensive with many bilateral air services agreements yet to be filed. It is relatively common for air services agreements to be in operational effect before all constitutional processes have been completed by the parties.
KLM S18 long-haul changes as of 26MAR17
14 hours ago