Generally speaking, it is ok to use a foreign currency credit card to buy domestic air tickets. However, it should be noted that different airlines and payment platforms may have different restrictions on foreign currency credit cards. Some may only accept certain types of foreign currency credit cards (such as US dollar credit cards), while others may accept all foreign currency credit cards. In addition, when using foreign currency credit cards for payment, you may need to pay extra fees, which may vary depending on the credit card type and payment platform. Therefore, before using a foreign currency credit card when purchasing domestic air tickets, it is best to know whether the credit card used is acceptable and consult relevant procedures and policies.