Online travel itinerary and trip planning service TripIt has launched a free iPhone application that displays a traveler's detailed itinerary on their mobile phone, so they have all their travel plans at their fingertips.

With the new TripIt for iPhone, travelers now have mobile access to all their TripIt itineraries, which can include travel plans from more than 500 booking sites. Travelers can find the travel details they need, whether their iPhone is online, offline or in airplane mode, and link to Web sites or call numbers from their itinerary.

"The key benefit of using a client app compared to our mobile Web app at m.tripit.com is the ability to store itineraries on the device for access offline," said Scott Hintz, cofounder of TripIt, San Francisco. "Because so many of our users are, not surprisingly, traveling, they often find themselves outside of WiFi or cell network coverage, but still need access to their travel information.

"Data roaming while outside your home country can also be very expensive, so that's another reason why so many TripIt travelers have been asking for a way to access their information without having to go online," he said.

"Building a client resident app also makes it easier to take advantage of some of the device's features, such as the iPhone's built-in mapping functionality."

While TripIt targets anyone who travels, currently the majority of trips being managed on TripIt are for business travel.

"Of course, the more you travel, the more value you get from the service, so it's not surprising that we appeal strongly to the road warrior audience," Mr. Hintz said.

"We have users from all 100 of the Business Travel News Top 100 corporations, based on total travel spend, plus many travelers from small and medium-sized businesses who rely heavily on TripIt's travel tools, since they don't have an in-house travel agency," he said.

TripIt helps people organize their travel plans no matter where they book by forwarding their travel confirmation emails to .

TripIt automatically creates a master itinerary that combines all their travel plans plus weather, maps and restaurants.

With TripIt, consumers can share and collaborate on travel plans with friends and colleagues.

TripIt is an open itinerary platform that supports more than 500 booking sites and can be accessed from mobile devices, calendars and blogs, as well as from partners including LinkedIn, Microsoft Windows Live and Plaxo.

TripIt for iPhone is available for free in the Apple iTunes App Store or at http://www.tripit.com/uhp/iphone. TripIt supports other mobile devices with a specially designed Web site at http://m.tripit.com.

Hertz, Travel Guard and Virgin America all have a strong presence throughout the TripIt site as part of their long-term sponsorships of TripIt.

They have prominent ad units on the main trip dashboard page users see when they log into TripIt, as well as right on the travel itinerary itself.

In addition, each sponsor is promoted in TripIt's emails and on its mobile site.

"For example, when a traveler sends his flight booking to to be added to his account, TripIt responds immediately with a confirmation email that may also include an offer for a Hertz rental car, making this a highly targeted and valuable opportunity for our sponsor to engage with the traveler," Mr. Hintz said.

"Hertz has also extended specially discounted rates for TripIt travelers, which can be accessed from links we've integrated into the TripIt itinerary," he said.

Frequent travelers can forward their travel confirmation emails to and automatically get their travel plans right on their iPhone.

TripIt for iPhone was created using the TripIt Application Programming Interface that enables developers to build on TripIt's open itinerary platform.

More than 100 developers are using the TripIt API to create travel services.

TripIt's iPhone app is off to a great start, already one of the top 10 most downloaded travel apps in the iTunes app store in its first week.

"We saw a lot of viral activity around the app before we even announced that it was available in iTunes," Mr. Hintz said. "Some TripIt users happened to stumble upon the app in iTunes and then they started telling friends about it, and we saw a lot of tweets about it in Twitter.

"A few days later, TripIt blogged that the app was available, we tweeted about it and we sent out an email to our entire opt-in list to announce its availability," he said. "There was a lot of pent-up demand from the TripIt user base for the app, so once we let folks know that it was available, it started to fly off the shelves!

"What was a little more surprising was how many new TripIt users have come to us as a result of our iPhone app -- showing up as a top travel app in iTunes, plus all the Twitter activity mentioning the app, has given us exposure to people who didn't even know about TripIt."