I was pleasantly surprised when A Fortean in the Archives linked (also here) to my recent post on Boer War airpower for several reasons. Firstly, because it's always nice to be linked to. Secondly, because I've been following A Fortean in the Archives for a while now: the Fortean in question is Mike Dash, a former contributing editor of Fortean Times who has a PhD in British naval history and has written a fine call-to-arms for Fortean historians called Borderlands, which deserves to be more widely read. And thirdly, because of the post itself, which is about the curious episode of Walter Powell, a Conservative MP who disappeared in 1881 when his balloon was swept out from Dorset over the English Channel. This was highly publicised in the press, and for the next week or so reports came in of sightings of Powell's balloon. Many were from fairly plausible locations (Dartmouth, Alderney, northern Spain), but a couple were from Scotland nearly a week later, which is not plausible at all. So in at least some cases, whatever they did see, it wasn't Powell in his balloon. This suggests that expectations were playing a role: having been told by the press that a balloon was lost at sea, people were apt to interpret anything aerial they didn't recognise (a planet, a Reticulan scoutship) as Powell in his balloon.
This is a useful reminder that phantom airship 'scares' were only incidentally due to fear; the real cause was expectation. An even clearer example comes from Canada in 1896. The context was the attempt by S. A. Andrée, a Swedish engineer, to reach the North Pole by air. His plan was to launch in a balloon from Danskøya, an island near Spitsbergen, and drift north with the wind. After reaching the pole, the balloon would eventually land in Canada or Russia. The Swedish and international press covered the preparations for the voyage in some detail. On 30 June, the balloon was inflated, and Andrée and his two companions announced their intention to start for the pole when the wind was favourable.
The very next day, some people in Winnipeg saw a balloon they identified as Andrée's, far off in the distance, which excited some comment in the press. More interestingly, on 3 July, the chief of the Kispiox people and a group of trappers saw something balloon-like, brightly-lit and travelling north while at Blackwater Lake in British Columbia. Not far away, on the Skeena river, an Aboriginal boy saw something very similar on the same date. Both of these reports were relayed through a local Indian Affairs agent, who had warned the locals that they were 'liable' to see Andrée's balloon travelling north over the next month, and presumably accepted the sightings as being reliable.
And so they did, or rather 'did', because Andrée's balloon never left the ground. The wind at Danskøya kept blowing steadily south, and the expedition was put off until the following year. Free ballooning was not at all common in the 1890s, and it's unlikely that anyone would have tried it over the wilds of British Columbia. So there was nothing to see along the Skeena, yet something was seen, precisely because something was expected.
The Andrée expedition did set off in 1897, on 11 July, but the balloon crashed into pack ice after only two days and 300 miles. Andrée and his companions tried to return on foot, but perished before reaching safety. Their fate was unknown until 1930. It will come as no surprise that more phantom sightings of Andrée's balloon were reported from Canada: this time from Rivers Inlet, Kamlooms [edit: more likely Kamloops], Victoria, Goldstream, Douglas, Winnipeg, Rossland, Souris and Honora. Most spectacularly, thousands of people in Vancouver saw 'a very bright red star surrounded by a luminous halo' to the south for a quarter of hour on 13 August, which again was identified with the now-wrecked Andrée balloon. With mystery aircraft, expectation is everything.
Source: Robert E. Bartholomew and George S. Howard, UFOs & Alien Contact: Two Centuries of Mystery (Amherst: Prometheus Books, 1998), chapter 3.