The attractiveness of the FA (key dependant variables are age and attitude) correlates negatively with the a/c sizes and length of flights (generally). The real young, cute and spunky ones, you would find them on RJs (yes) and 733s and 735s, most probably.

If someone fall for FC FA on international routes, either the FAs aged really well and carry the airline allure with them (the allure does not go away with age btw), or it just reveals the age of pax who hits on the FAs.