That spring, no true Englishman could enjoy an evening stroll without spotting a zeppelin. “My eye was at once attracted by a powerful light, which I should judge to have been some 1,200 feet above the ground,” said Police Constable Kettle of his March 23, 1909 sighting, reported in London’s Daily Mail. “I also saw a dark body, oblong and narrow in shape, outlined against the stars.” His observation was seconded by a Miss Gill, who told the Evening News of “a brilliant flashing light in the sky.”

Zeppelins had been flying for nine years, but this was the first time one had been spotted over England. Designed by Count Ferdinand Graf von Zeppelin, the rigid airships were marvels of engineering: 446 feet long, built of 16 linked duralumin rings braced with wire and girders to hold bags of hydrogen in place, the whole structure covered with a cotton skin. But they had also proven fragile, skittish, and prone to catastrophe: Of the first 10 built, six crashed or burned. By 1909, only two, LZ 3 and LZ 4, had enjoyed some success. LZ 3 made 45 short hops totalling 2,733 miles, while in 1908, LZ 4 made a 12-hour trip of more than 600 miles. But had one really flown from the zeppelin hangar at Friedrichschafen, Germany, to Peterborough, England, and back—a trip of 1,036 miles?

British newspapers continued to report airship sightings: one in Cambridgeshire, another by two constables in Ipswich, an egg-shaped ship over Suffolk. In May, says historian Brett Holman of the University of Melbourne in Australia, who has catalogued the reports, London newspapers carried 49 sightings, including a May 18 account of railroad signalmen seeing “a boat or cigar shape” over Cardiff, in Wales. A zeppelin was even spotted over Ireland, where, according to the Belfast Telegraph, “the aerial visitant was thousands of feet light [high], and came steadily in the direction of the city.”

The sightings caused the British terrible anxiety. At the time, Germany and the United Kingdom were locked in an arms race. In 1906 the British had commissioned the Dreadnought, the fastest battleship in the world, and the most sophisticated in firepower. Germany would launch a fleet of formidable Kaiser-class battleships, but it hoped to shore up its naval power with airships. In 1908, German privy councillor Rudolph Martin bragged to Daily Mail readers that in the event of a war, a zeppelin fleet would “transport 350,000 men in half an hour during the night from Calais to Dover…. [W]e would conclude no peace until a German army had occupied London.”

Popular culture reflected Germany’s threat. The year before the airship reports, the British magazine Pall Mall had serialized H.G. Wells’ The War in the Air, a novel in which a fleet of German dirigibles bombs New York. The following year, Martin elaborated on his boasts, publishing World War in the Air, a book that imagines zeppelins bombing block after block of Paris (“Even at high altitudes,” says one character, “I heard the sounds of hundreds of people crying for help”) and defeating England.

The British “woke up to the idea that the Germans had created this dreadful weapon capable of breaking the [protective] barrier of the British navy,” says folklorist David Clarke of the University of Sheffield. “[F]or the first time in its history the island was vulnerable to invasion from the air.”

The sightings went on for four months, with several hundred people throughout the United Kingdom reporting lights and zeppelin-like objects in the sky. Were they on to something?

In truth, the odds of spotting a real zeppelin over the British Isles in 1909 matched the likelihood of seeing Kaiser Wilhelm dancing the can-can at a Paris burlesque house. “No airships could have possibly invaded then,” says historian Guillaume de Syon, author of Zeppelin! Germany and the Airship, 1900–1939. The engines were reliable only in failing, he adds. Furthermore, zeppelin pilots navigated “by observing the roads or looking for landmarks like a church steeple,” says de Syon, and those would have been in short supply as a London-bound zeppelin crossed the North Sea. The journey would also carry the ship over Belgium and France in daytime (zeppelins then did not fly at night), creating an international incident at a time when every visit of dirigibles to Europe’s skies brought thousands of people streaming into the streets.

Many historians, Clarke says, think the airship scare was worked up by newspapers such as the Daily Mail, owned by Alfred Charles William Harmsworth, known as Lord Northcliffe. The phantom airship reports spiced up the paper’s usual fare and put pressure on the government to increase military spending (one of Lord Northcliffe’s preoccupations). And with papers reporting airship spottings day after day, says Clarke, “you get this huge popular delusion.”

On the other hand, some papers were openly skeptical about the reports. The Weekly Dispatch noted that in one case, an airship was seen at Stamford and 20 minutes later over the coast at Southend; “this would give the airship a speed of 210 miles per hour seeing as the two places are seventy miles apart.” For airships of the day, a speed of 40 mph was more like it.

Newspapers also reported cases in which witnesses refuted zeppelin sightings. Daniel Blight told the South Wales Daily Post, “The airship was of quarter-circle shape, with two bright lights, one at each end of it…. I drew the attention to it of Constable No. 440C., who was passing at the time, and no doubt he will report it.” But the paper also quoted Constable 440C. saying that what he saw that night was “a particularly bright star, and it was there again on Thursday night.”