International Consolidated Airline Group (IAG) said it carried 4.2 per cent more passengers in March to 5.68m compared to the same month a year ago.The load factor, which measures the number of passengers to number of seats, fell 2.2 percentage points to 77.6%. In the year-to-date passengers numbers climbed 5.9% year-on-year to 15.28m. The load factor fell 0.7 percentage points to 76.7%.The parent company of British Airways revealed traffic, measured in revenue passenger kilometres, increased by 10.2% in March on the year. The group said traffic and load factor were affected by the timing of route launches this month, and Easter, which fell in March last year, but falls in April this year.Underlying market conditions remain unchanged from those published at full-year 2013 results, IAG added. IAG also announced British Airways and Iberia's joint business with American Airlines has been extended to include US Airways. The revenue sharing agreement now includes all scheduled flights operated by American and US Airways, British Airways, Iberia and Finnair between North America and Europe. "US Airways brings 28 flights into the joint business, of which 27 are new, and gives customers of British Airways and Iberia access to more than 50 additional new destinations in North America," IAG said.According to broker Renta 4, in Madrid, the above figures were slightly lower than what had been implied by the carrier's forecasts for the first quarter. Nonetheless, the firm maintained its targets for the full-year, the broker pointed out. Shares rose 0.30% to 437.80p at 15:57 on Thursday.RD