Originally "flash video" was Sorenson Spark/H.263, in 2005 they added On2's VP6 which was their high quality option until they added H.264 a couple of years later. Each step improved quality but mostly by adding decode complexity so as computers have got faster people have migrated to the heavier-weight codecs.

I would imagine that today all but legacy content served via Flash on the web is a standard H.264 file that can be easily repurposed for serving via HTML5 to Safari and newer iDevices (older ones only supported the lower profiles).