Major airline companies flying different planes across the country, what are the safety implications?

So you've booked a flight home for the holidays. The flight number on your receipt shows you're flying on one of the nation's major airlines. You check in at its terminal. You proceed to one of its gates. And when you board, the aircraft is painted with the colors and logo of the major carrier.
But if you read the fine print when you book -- or check the asterisk on your e-mailed receipt -- you could well find you're flying on a plane owned and operated by somebody else. Often, it's an obscure regional airline.
This system is known as code-sharing. Major airlines insist it presents travelers with a "seamless" experience. It also presents a truth-in-advertising problem. Imagine, for instance, how you'd feel if you bought a ticket to a Philadelphia Phillies game and, when you got to the ballpark, the Phillies' Triple A farm team, the Lehigh Valley IronPigs, took the field instead.

Link:
http://blogs.usatoday.com/oped/2009/12/debate-on-air-travel-our-view-when-airlines-share-codes-truthinlabeling-suffers.html?loc=interstitialskip