I have not had a problem receiving multiple bonuses on the same account. Here's how I have done it.
Sign up for a Delta Amex card. Use it for 11 months. Call Amex and ask to switch to Hilton HHonors no fee card. Wait at least a year and switch back to Delta. Each time, I have received the bonus as if I was applying for a new card. Keep in mind that your account number does change each time you switch affinity.
Don't confuse this strategy with my previous post as that was simply a new application/card. I simply wanted the 15k bonus miles but have no need for a second Amex card.
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"You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer." - Frank Zappa (1940-93)
[This message has been edited by MileageAddict (edited Feb 21, 2004).]