High, high above the North Pole, on the first day of1969, two professors of English literature approached each other at a combined velocity of 1,200 miles per hour. They were protected from the thin, cold air by the pressurized cabins of two Boeing 707s, and from the risk of collision by the prudent arrangement of the international air corridors. Although they had never met, the two men were known to each other by name. They were, in fact, in process of exchanging posts for the next six months, and in an age of more leisurely transportation the intersection of their respective routes might have been marked by some interesting human gesture: had they waved, for example, from the decks of two ocean liners crossing in mid-Atlantic, each man simultaneously focusing a telescope, by chance, on the other, with his free hand; or, more plausibly, a little mime of mutual appraisal might have been played out through the windows of two railway compartments halted side by side at the same station somewhere in Hampshire or the Mid-West, the more self-conscious party relieved to feel himself, at last, moving off, only to discover that it is the other man's train that is moving first...However, it was not to be. Since the two men were in airplanes, and one was bored and the other frightened of looking out of the window "since, in any case, the planes were too distant from each other to be mutually visible with the naked eye, the crossing of their paths at the still point of the turning world passed unremarked by anyone other than the narrator of this duplex chronicle.

　　"Duplex" as well asshavingsthe general meaning of "two-fold" applies in the jargon of electrical telegraphy to "systems in which messages are sent simultaneously in opposite directions"(OED). Imagine, if you will, that each of these two professors of English Literature (both, as it happens, aged forty) is connected to his native land, place of employment and domestic hearth by an infinitely elastic umbilical cord of emotions, attitudes and values "a cord which stretches and stretches almost to the point of invisibility, but never quite to breaking-point, as he hurtles through the air at 600 miles per hour. Imagine further that, as they pass each other above the polar ice-cap, the pilots of their respective Boeings, in defiance of regulations and technical feasibility, begin to execute a series of playful aerobatics "criss-crossing, diving, soaring and looping, like a pair of mating bluebirds, so as thoroughly to entangle the aforesaid umbilical cords, before proceeding soberly on their way in the approved manner. It follows that when the two men alight in each other's territory, and go about their business and pleasure, whatever vibrations are passed back by one to his native habitat will be felt by the other, and vice versa, and thus return to the transmitter subtly modified by the response of the other party "may, indeed, return to him along the other party's cord of communication, which is, after all, anchored in the placeswhereshe has just arrived; so that before long the whole system is twanging with vibrations travelling backwards and forwards between Prof A and Prof B, now along this line, now along that, sometimes beginning on one line and terminating on another. It would not be surprising, in other words, if two men changing places for six months should exert a reciprocal influence on each other's destinies, and actually mirror each other's experience in certain respects, notwithstanding all the differences that exist between the two environments, and between the characters of the two men and their respective attitudes towards the whole enterprise.

　　One of these differences we can take in at a glance from our privileged narrative altitude (higher than that of any jet). It is obvious, from his stiff, upright posture, and fulsome gratitude to the stewardess serving him a glass of orange juice, that Philip Swallow, flying westward, is unaccustomed to air travel; while to Morris Zapp, slouched in the seat of his eastbound aircraft, chewing a dead cigar (a hostess has made him extinguish it) and glowering at the meagre portion of ice dissolving in his plastic tumbler of bourbon, the experience of long-distance air travel is tediously familiar.

　　Philip Swallow has, in fact, flown before; but so seldom, and at such long intervals, that on each occasion he suffers the same trauma, an alternating current of fear and re-assurance that charges and relaxes his system in a persistent and exhausting rhythm. While he is on the ground, preparing for his journey, he thinks of flying with exhilaration "soaring up, up and awaysintosthe blue empyrean, cradled in aircraft that seem, from a distance, effortlessly at home in that element, as though sculpted from the sky itself. This confidence begins to fade a little when he arrives at the airport and winces at the shrill screaming of jet engines. In the sky the planes look very small. On the runways they look very big. Therefore close up they should look even bigger but in fact they don't. His own plane, for instance, just outside the window of the assembly lounge, doesn't look quite big enough for all the people who are going to getsintosit. This impression is confirmed when he passes through the tunnelsintosthe cabin of the aircraft, a cramped tube full of writhing limbs. But when he, and the other passengers, are seated, well-being returns. The seats are so remarkably comfortable that one feels quite content to stay put, but it is reassuring that the aisle is free should one wish to walk up it. There is soothing music playing. The lighting is restful. A stewardess offers him the morning paper. His baggage is safely stowed away in the plane somewhere, or if it is not, that isn't his fault, which is the main thing. Flying is, after all, the only way to travel.