It refers to "владельцам". "Им и самим" = "им самим". "И" is added for emphasis.
"The plane owners believe that such an airliner will be of use to them too..." (or "to them themselves")

It's a very common expression, which can be used when someone does something too. In this case voice sress is on "сам".
Он (и) сам не может этого сделать ~ He can't do it either (i.e. someone else mentioned before could not do it as well).
Я (и) сам этого не понимаю (~I don't understand it myself)