ExxonMobil has once again surpassed Apple as the world's most valuable company after the iPhone and iPad maker saw its stock price falter.

Apple's stock has been on the decline since the company's quarterly earnings report on Wednesday suggested that its fast growth phase, rare for a company of its size, may be coming to an end.

Apple's stock dropped 2.4 per cent to $439.51 in mid-day trading yesterday for a market capitalisation of $412.7 billion.

That followed a 12 per cent drop on Thursday, the biggest one-day percentage drop for the company since 2008.

ExxonMobil gained 22 cents yesterday to $91.57 for a market capitalisation of $417.5 billion.

Apple first surpassed Exxon in the summer of 2011. The two companies traded places through that fall, until Apple surpassed Exxon for good in early 2012.

Apple's stock price peaked in September at $705.07 on the day the iPhone 5 was released. Exxon, in the meantime, has been trading steady. Its business - oil - seems less prone to stock market ups and downs than the Cupertino, California-based tech darling.

Apple's stock price slipped below $500 for the first time last week, as investors saw signs that the iPhone 5 was falling behind competition from phones running Google's Android software, especially those from Samsung Electronics.-Reuters