Some analysts had expected the fall to be closer to 30%.
Ahead of the release of the traffic statistics, BA shares had fallen sharply, but the smaller than expected traffic fall lifted the stock back into the black.
The share slide during morning trade had prompted observers to predict that the airline might be relegated from the FTSE index of the UK's 100 leading shares.
Weak future
BA's share fell 9% in early trading on Monday after several major investment banks expressed concern about its performance.
Even BA itself appeared pessimistic about the immediate future, though bookings could pick up by the end of the year, the company said in its traffic statement.
"Forward bookings for November indicate a similar traffic decline to October, with the US, Middle East and Japan being the worst affected markets," BA said.
But "early indications for December suggest a slight improvement on November", the airline said.
The share price bounced back from Monday's early low of 133p to about 140p per share around lunchtime, about 5% below the opening price.
"At the current share price, BA could be out of the FTSE," said Barclays Stockbrokers transport analyst Anthony Cross.
But soon after, the stock rose to 149p by 1550 GMT, 1.5% above its opening price.
Less traffic
Mr Cross predicted that passenger numbers on trans-Atlantic flights would have stabilised after having fallen sharply since 11 September.
But traffic has deteriorated in Europe and other regions every single week since the attacks, he said.
BA will release its financial results for the first half of the fiscal year on Tuesday.
The figures will reveal the impact on BA's bottom line of the 11 September attacks and the subsequent war against terrorism.
Analysts predict more bad news from the airline.
Gloomy analysts
The initial fall in BA's share price came after Goldman Sachs described BA as a "market under performer" and said its shares are worth much less than the current market value.
Goldman predicted that BA would make pre-tax losses of £594m for the fiscal year ending on 31 March 2002.
Merrill Lynch raised its pre-tax loss forecast for the airline from £65m to £775m before exceptional items for the fiscal year.
Goldman Sachs valued the stock at between 55p and 128p.
Barclays Stockbrokers valued BA shares at around 100p.