Originally Posted by UnitedSkies
AFAIK, all Mileage Plus promotions codes do not have to be entered into fare search areas. Those "promotion/e-certificate codes" boxes are for discounts or other electronic vouchers.
What's MPW124, btw?
Incorrect. Entering MP promo codes will show flights which qualify for that particular promotion.
IIRC, MPW124 was the double miles promo. I think the booking period has ended though.