With a flurry of corporate earnings and the Federal Reserve's Biege Book on the cards for Wednesday's session, US stock futures were pointing to a flat start.

Investors are concerned that a slowing global economy will have an impact on company profits in the third quarter, particularly after the International Monetary Fund (IMF) slashed its growth forecasts the world over yesterday.

The Fed's Biege Book on economic conditions is due to be released at 14:00 in New York.

Alumnium giant Alcoa kicked off third-quarter earnings season last night by beating analysts' estimates. The company reported earnings per share (EPS) excluding charges of $0.03, surprising analysts who had expected a break-even result. Sales fell 8% year-on-year to $5.8bn but still beat the $5.56bn forecasts.

However, the company did cut its full-year global aluminium demand growth guidance from 7% to 6%, causing shares to dip in pre-market trade.

Yum! Brands saw futures rise strongly after saying last night that EPS came in at $1, better than the $0.97 estimate. The company also raised its full-year EPS growth target rate to at least 13%.

Oil giant Chevron was under pressure after earnings were hit by lower production, cure prices and US refining returns.

Retailing firm Costco was rising before the bell after beating expectations: EPS came in at $1.39, ahead of the $1.31 estimate.

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