This is what EF lists AY interline for baggage:
MAY CHECK BAGGAGE TO
AA AF AI AS AT AY AZ A3 BA BL BR BT B2 B6
CA CI CX CZ DE DL DX EI EK EY FB FI FJ FM
GA GK HG HO HR HU HX IB JC JJ JL JQ JU KE
KL KM KU LA LH LO LP LX LY ME MF MH MS MU
NH NT NU NZ OA OS OU OZ PG PR PS PX PZ QF
QR SB SK SN SQ SU S7 TG TK TN TP UA UK UL
U6 VN VS WF WS W2 XL YO ZH 0B 2N 3K 3U 4M
9W