No words excite me more than "free first class upgrade." It’s one of the reasons I became a travel agent back in the day when travel agents heard them regularly. But for the last two decades, the surest route to the front cabin has been frequent flier miles.  Which is why I live by the manta "every mile is sacred."  I’ve already written about the Starwood Preferred Guest American Express Card, which is hands-down the best mile-earning card around.  But my friend David tipped me off to this current offer for the Chase United Mileage Plus Visa card.  25,000 bonus miles for new accounts when you spend $250 on the card.  And no annual fee for the first year.  At a street value of 2¢/mile, that’s $500 — the richest sign-up bonus I’ve ever seen.  And used for a free ticket or upgrade, it’s worth even more.