A jet aircraft, flying from Goose Bay, Labrador, to Fairbanks, Alaska, made auroral observations at nearly constant magnetic local time (~2100 MLT) in the auroral zone while a Vela satellite passed through the plasma sheet at r?18RE at nearly the same magnetic local time. Comparison of data from the two locations provide further confirmation of the 'poleward leap' of the auroral electrojet which occurs in a late phase of an auroral substorm and is associated with a rapid tailward motion of an X-type neutral line in the magnetotail. The poleward leap is a a distinctive feature of the substorm evolution and is not simply the superposition of a new substorm on the recovery phase of a preceding substorm. It probably marks the sudden transition of the magnetotail from one quasi-stable configuration to another more stable one. Onset of a substorm expansive phase brings about a change of tail magnetic field from a configuration that is extremely tailike, with field lines from &lgr;m≲66¿ stretching to the Vela orbit, to one that is much less taillike, with field lines from &lgr;m>70¿ not stretching as far as the Vela orbit.