Several airlines have recently announced plans to expand their onboard Wi-Fi offerings. Some 1,800 main-line aircraft out of 3,500 offer Wi-Fi, said Amy Cravens, an analyst at market-research company In-Stat. Experts say that carriers with Wi-Fi may be more attractive to business travelers. "Wi-Fi can be the cherry on the icing on the cake," noted Henry Harteveldt, co-founder of Atmosphere Research Group. "That's especially true for people who are in sales or consulting, where time literally is money. These guys want -- and need -- to be online."