CHICAGO, Feb 21 (Reuters) - UAL Corp.'s (UAL) United Airlines, the No. 2 U.S. carrier, said on Thursday it is recalling 1,200 furloughed flight attendants to keep up with its increased April flight schedule. The airline, which earlier this week tentatively agreed to a new contract for 13,000 mechanics and cleaning staff, said the new recalls bring the number of flight attendants back on the payroll since Jan. 31 to 2,000. United recently announced it was adding 127 flights to its April schedule in certain markets, in keeping with other gradual restoration of some flights industrywide since the Sept. 11 attacks. It plans to furlough fewer pilots as well. After the attacks, United laid off about 20 percent of its work force, including 2,700 flight attendants.