I've had the American Express Platinum Card® for the best part of a decade, and for most of that time, United Airlines has been my selected airline for the card's up to $200 annual airline fee statement credit (enrollment required).It was the right choice then.Earlier this year, I used part of my 2026 credit toward a United Economy Plus seat assignment on a flight to Mexico.United Economy Plus seats. ZACH HONIG/THE POINTS GUYA few months later, …