"SEC. 1112.(a) No part of the compensation paid by any air carrier to an employee who performs his regularly assigned duties as such an employee on an aircraft in more than one State shall be withheld for income tax purposes pursuant to the laws of any State or subdivision thereof other than the State or subdivision wherein more than 50 per centum of the compensation paid by the carrier to such employee is earned: Provided, however, That if the employee did not earn more than 50 per centum of his compensation from said carrier in any one State or subdivision thereof during the preceding calendar year, then withholding shall be required only for the State or subdivision of the employee's residence, as shown on the employment records of any such carrier; nor shall such carrier file any information return or other report for income tax purposes with respect to such compensation with any State or subdivision thereof other than such State or subdivision of residence and the State or subdivision for which the withholding of such tax has been required under this subsection. "(b) For the purposes of subsection (a), an employee shall be deemed to have earned 50 per centum of his compensation in any State or subdivision in which his scheduled flight time in such State or subdivision is more than 50 per centum of his total scheduled flight time in the calendar year while so employed. "(c) For the purposes of this section the term 'State' also means the District of Columbia and any of the possessions of the United States; and the term 'compensation' shall mean all moneys received for services rendered by an employee, as defined in subsection (a) in the performance of his duties and shall include wages and salary."