610 § 502. Required drills and field exercises (a) Under regulations to be prescribed by the Secretary of the Army or the Secretary of the Air Force, as the case may be, each company, battery, squadron, and detachment of the National Guard, unless excused by the Secretary concerned, shall— (1) assemble for drill and instruction, including indoor target practice, at least 48 times each year; and (2) participate in training at encampments, maneuvers, outdoor target practice, or other exercises, at least 15 days each year. (b) An assembly for drill and instruction may consist of a single ordered formation of a company, battery, squadron, or detachment.^ or, when authorized by the Secretary concerned, a series of ordered formations of parts of those organizations. However, to have a series of formations credited as an assembly for drill and instruction, all parts of the unit must be included in the series within seven consecutive days of the same calendar month. (c) The total attendance at the series of formations constituting an assembly shall be counted as the attendance at that assembly for the required period. No member may be counted more than once or receive credit for more than one required period of attendance, regardless of the number of formations that he attends during the series constituting the assembly for the required period. (d) No organization may receive credit for an assembly for drill or indoor target practice unless— (1) the number of members present equals or exceeds the minimum number prescribed by the President; (2) the period of military duty or instruction for which & member is credited is at least one and one-half hours; and (3) the training is of the type prescribed by the Secretary concerned. (e) A n appropriately rated member of the National Guard who performs an aerial flight under competent orders may receive credit for attending drill for the purposes of this section, if the flight prevented him from attending a regularly scheduled drill. § 503. Participation in field exercises (a) Under such regulations as the President may prescribe, the Secretary of the Army and the Secretary of the Air Force, as the case may be, may provide for the participation of the National Guard in encampments, maneuvers, outdoor target practice, or other exercises for field or coast-defense instruction, independently of or in conjunction with the Army or the Air Force, or both. (b) Amounts necessary for the pay, subsistence, transportation, and other proper expenses of any part of the National Guard of a State or Territory, Puerto Rico, the Canal Zone, or the District of Columbia participating in an exercise under subsection (a) may be set aside from funds allocated to it from appropriations for field or coast-defense instruction. (c) Members of the National Guard participating in an exercise under subsection (a) may, after being mustered, be paid for the period beginning with the date of leaving home and ending with the date of return, as determined in advance. I f otherwise correct, such a payment passes to the credit of the disbursing officer.