Delta and United have barred passengers from taking robots that resemble humans or animals on flights, whether in the cabin or as checked baggage. The move reflects airlines’ concerns that the large lithium-ion batteries commonly used in such machines could create a fire risk, adding a new restriction as humanoid robots become more visible in public settings.

Delta says the ban is temporary and applies to robots that imitate a human or animal in appearance, size, movement or behaviour. Small toy versions remain permitted if they meet normal hand-luggage, stowage and battery rules; Delta generally permits lithium-ion batteries of up to 160 watt-hours, while defective or recalled batteries are prohibited.