Since you mention that you may be building a screen scraper that gathers airline fares, you may be interested to know that American Airlines has already sued (and won a preliminary injunction against) a software company that built a tool that does much the same thing. The case is American Airlines v. FareChase, and was discussed on LawMeme:
American... sued FareChase in a Texas court (American is based in Dallas, so that's its home turf) and got a preliminary injunction against FareChase's screen-scraping practices. The court decided that the screen-scraping constituted an "interfer[ence] with American's personal property," also known these days as a trespass to chattels. The court also noted that FareChase's actions might be a criminal violation of Texas Law, which states, "A person commits an offense if the person knowingly accesses a computer, computer network, or computer system without the effective consent of the owner." Tex. Penal Code 33.02(a).
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Since you mention that you may be building a screen scraper that gathers airline fares, you may be interested to know that American Airlines has already sued (and won a preliminary injunction against) a software company that built a tool that does much the same thing. The case is American Airlines v. FareChase, and was discussed on LawMeme:
The injunction order is posted on EFF's site, and the briefs are posted on Bag & Baggage.