Cyberattack is the first thought that comes to mind when computer systems fail. It was certainly the presumption when, within hours last week, the US' largest airline, biggest stock exchange and most influential business newspaper suffered disruptions. Investigations have since shown that technology glitches, not hacks, were involved and that the timing was mere coincidence. Rarely has there been a better lesson about the need not to jump to conclusions and of ensuring old ways of doing business are not forgotten.

United Airlines was the first hit at 8am, with services suspended for two hours, leading to 800 flight delays and 60 cancellations. Trading on the New York Stock Exchange was shut from 11.30am for four hours by what was labelled a "technical issue". About 20 minutes after it went down, the home page of the became unavailable. Unsurprisingly, the timing and the prominence of the firms prompted speculation that the incidents were related and involved an attack on the US from another country. China was the immediate suspect; just last week, Democratic presidential candidate Hillary Clinton accused it of attacking American networks to steal information and gain economic and military advantages. Beijing rejected the accusations.

Hacking has been discounted. A router failure was behind United's problems, a computer glitch hit the stock exchange and it appears the 's system ground to a halt after becoming overloaded - perhaps due to readers seeking information about the NYSE. Like other companies with large computer systems, all have previously experienced difficulties. While problems were being fixed, the NYSE was able to route business to other exchanges and the newspaper put up a rudimentary replacement site.