The early aircraft cruiser turned out to be an unsuccessful design. The rapid development of naval aircraft in the 1930s quickly rendered the vessels obsolete and they were rebuilt e.g. as anti-aircraft cruisers. A more modern derivative of the aircraft cruiser is the helicopter cruiser. The Invincible-class aircraft carriers of the Royal Navy can also be considered; they were originally classed as cruisers due to their original role as command and control platforms as well as ASW vessels, taking on those roles from the RN's "Tiger" class cruiser conversions).