No issue. It'll apply the ecredit to the new ticket for each passenger. Each passenger has their own ticket. Whatever value of ecredit in their name will come off that person's ticket. This means if tickets cost say $200 per passenger, and you have $150 ecredit for each passenger, plus a 2nd $100 ecredit for just one of the passengers, one passenger would be paid in full, the other would need to pay $50. (The remaining $50 ecredit for the one passenger can only be applied to a ticket in their name, it couldn't be used to cover the remaining $50 for other passenger)