Google Inc is deploying a fleet of small, camera-equipped airplanes above several cities, the Internet search company's latest step in its ambitious and sometimes controversial plan to create a digital map of the world.

Google plans to release the first three-dimensional maps for several cities by the end of the year, the company said at a news conference at its San Francisco offices on Wednesday.

Google declined to name the cities, but it showed a demonstration of a 3D map of San Francisco, in which a user can navigate around an aerial view of the city.

"We're trying to create the illusion that you're just flying over the city, almost as if you were in your own personal helicopter," said Peter Birch, a product manager for Google Earth.

Google's head of engineering for its maps product, Brian McClendon, said the company was using a fleet of airplanes owned and operated by contractors and flying exclusively for Google.

Asked about potential privacy implications, McClendon said the privacy issues were similar to all aerial imagery and that the type of 45-degree-angle pictures that the planes take have been used for a long time.

Google has used airplanes to collect aerial photos in the past, such as following the 2010 San Bruno, Calif. gas-line explosion, but the latest effort marks the first time the company will deploy the planes in a systemic manner to build a standard feature in one of its products.

By the end of the year, Google said it expects to have 3D map coverage for metropolitan areas with a combined population of 300 million people. The first 3D cityscape will be available within weeks.

Google has for years operated a fleet of camera-equipped cars that crisscross the globe taking panoramic pictures of streets for its popular mapping service. The cars have raised privacy concerns in some countries.

In 2010, Google acknowledged that the so-called Street View cars had been inadvertently collecting emails, passwords and other personal data from people's home wireless networks. Collecting the WiFi data was unrelated to the Google Maps project, and was done instead so that Google could collect data on WiFi hotspots that can be used to provide separate location-based services.

The forthcoming 3D city maps will be part of the Google Earth software app available for mobile devices such as smartphones based on Google's Android software and Apple's iOS software.

The company also announced a version of Google maps for Android smartphones that allows users to access certain maps without an Internet connection.

Shares of Google finished Wednesday's regular session up 1.8 percent at $580.57.

Google's announcement comes a week before Apple Inc's developer conference in San Francisco, as competition between the two tech giants continues to heat up, particularly in the fast-growing mobile market.

Apple is planning to replace Google Maps as the built-in mapping service on its iPhone and iPad later this year with technology that it has created in-house, according to media reports. Apple could show off its new mapping software at next week's conference.

Google's McClendon said the company would continue to make Google maps services available as widely as possible, on "all platforms."

In what appeared to be a veiled jab at Apple, he said the integration with Google's search engine provides a mapping serving that is far more useful than a product that simply uses a "geocoder" -- technology that uses geographic coordinates to create a digital map. Apple began to use its own geocoder technology for the Google-based maps on its smartphones late last year.

Google said on Wednesday that there are currently 1 billion monthly active users of Google maps services and that the Street View cars have driven more than 5 million miles (8 million km) Photographing streets all over the world.

Asked if Google had any plans to use unmanned aerial drones to gather photos for its 3D cityscapes, McClendon said it was an interesting question, but noted that drones were still being evaluated by the Federal Aviation Administration.

"That's a larger can of worms that we're not going to get into here," he said.