Based on the April 24, 1960 BOAC schedule (Section: Britain – East & Central Africa) linked below, it is possible, for example, that Ann Dunham and her new baby took BOAC Flight BA162 (Sunday or Wednesday) in August 1961 on a ‘Bristol Britannia Turboprop Aircraft’ which departed Nairobi at 20.30 (GMT +3), made stops in Entebbe, Khartoum, and Rome, and arrived in London at 12.35 (GMT +1) on the next day. Thus, the total flight time was just slightly over 18 hours. Two main meals and a breakfast were served on the flight. Britannia Flight BA160 (Thursday or Saturday), another possibility, did not stop in Entebbe and therefore arrived in London a few hours earlier.
As another possibility, Ann and her newborn son could have taken BOAC Flight BA116 (Monday, Tuesday, Friday, Saturday and Sunday) on a 'de Havilland Comet 4 Jet Aircraft', which departed Nairobi at 3:35 (GMT+3), made stops only in Khartoum and Rome, and arrived in London at 14.15 (GMT+1). The total flight time for this option was just slightly under 13 hours. A breakfast and a main meal were served on the flight. Comet 4 Flight BA122 (Wednesday), another possibility, had the same flight time of slightly under 13 hours.
http://www.timetableimages.com/ttimages/complete/ba60/ba60-12.jpg
Images of the BOAC air routes (world & africa respectively), published April 24, 1960:
http://www.timetableimages.com/ttimages/complete/ba60/ba60-13.jpg
http://www.timetableimages.com/ttimages/complete/ba62/ba62-36.jpg
Speculation regarding the possible flight by Ann Dunham with her new baby boy, BHO-II, in August 1961 from London to Vancouver, Canada, prior to their trip to Seattle, Washington where she started attended night school extension classes at the University of Washington in the Fall Semester.
Based on the April 24, 1960 BOAC schedule (Section: Europe - Britain - Ireland - Canada - USA) linked below, it is possible, for example, that Ann Dunham and her new baby son took Trans Canada Flight TC541 (Wednesday) in August 1961 on a Lockheed ‘Super Constellation’ which departed London (North Side) at 17.00 (GMT +1), made stops in Glasgow, Scotland, Winnepeg, Canada, and arrived in Vancouver at 7.40 (GMT -7) on Thursday morning. Thus, the total flight time for the trip was just slightly under 23 hours.
http://www.timetableimages.com/ttimages/complete/ba60/ba60-02.jpg
Freepmail on the way.