The differences between domestic and international airfares
are largely due to the differences in how they are, or are
not, regulated. Unlike deregulated domestic USA airfares,
international airfares are regulated both by international
treaties and by an international airline price-fixing
cartel, the International Air Transportation Association
(IATA).
It's worth noting that *every* USA-based airline operating
scheduled international passenger flights has *voluntarily*
joined IATA. USA airlines' invocations of "open markets",
"free trade", and "open skies" can be dismissed as
completely hypocritical and self-serving drivel until such
time as they exercise their right to withdraw from IATA, as
any of them could at any time. USA airlines are allowed to
participate in IATA "traffic conferences" only because of a
special exemption granted them from USA anti-trust laws which
normally forbid such industry-wide collusion on prices.