An apparatus and method for supplying oxygen to passengers on board an aircraft includes a portable machine (10), which has a shape and size to be positioned under a seat of the aircraft. Within the housing of portable machine (10) are mounted an air separation device (86) for separating oxygen from air inside the aircraft,an air supply device (88), a timing and control device (90), and a circuit board (92). Air supply device (88) includes a compressor (96) operatively connected to air separation device (86) and a brushless d-c motor (98) for driving compressor (96). Circuit board (92) connects the motor (98) to an aircraft electrical power source (191). Brushless d-c motor (98) insures compliance with airline requirements that machine (10) generates a low level of electrical interference. Portable machine (10) has the capability of delivering oxygen at various predetermined flow rates easily manually selected by a user.