HOLLYWOOD, May 15— Summer begins early in Hollywood. The 16 glorious weeks when movie theaters are expected to sell well over $1 billion worth of tickets started last Friday with the release of ''Blue Thunder'' and ''Breathless.''

Last summer was the most successful in movie industry history, with nearly $1.4 billion worth of tickets sold. This summer is expected to be even better because among the releases will be the third ''Star Wars'' movie - ''Return of the Jedi,'' the third Superman movie - ''Superman III'' and the 13th film in the James Bond series - ''Octopussy.''

The industry feels certain that all three movies will have enormous success. The biggest concern, however, is that, like immense trees, they may block out the sun for most of the other 37 movies the major studios expect to release this summer. Because films can shrivel when placed in the shadow of the giants, a lot of studio planning has gone into giving them the necessary space to grow. Starring Several Helicopters

''We released 'Blue Thunder' last weekend so it would be established before 'Jedi,' '' said Frank Price, chairman of Columbia, about his studio's hard-edged action movie starring Roy Scheider and several helicopters. ''We have a space movie, too, 'Spacehunter, Adventures in the Forbidden Zone.' How do we make 'Spacehunter' special? By making it in 3-D. And we're releasing it on May 20, one week before 'Jedi.' ''

''There's a tremendous amount of jockeying for position going on this summer,'' said Barry Reardon, president of distribution at Warner Bros. ''It's almost like television network counterprogramming. Originally, we had our Steve Martin movie, 'The Man With Two Brains,' scheduled for June 10 and 'Superman' on June 17. M-G-M/U.A. had 'WarGames' on June 10 and 'Octopussy' June 17. Then M-G-M/U.A. moved 'WarGames' up to June 3 and 'Octopussy' to June 10 to get out of the way of 'Superman' and we moved 'The Man With Two Brains' to June 3 to get out of the way of 'Octopussy,' '' he said. ''Octopussy,'' with Roger Moore as 007, will be followed next fall by another Bond movie, ''Never Say Never Again,'' with Sean Connery returning to the role he created.

''Superman III'' will have the marketplace to itself on June 17, and no other studio is brave enough to compete with 20th Century-Fox's ''Return of the Jedi'' on May 25. Although, as Mr. Price said, ''it's going to be very hard to dodge the competition this summer,'' one tactic is to allow ''Jedi'' and ''Superman'' several weeks to cool down. Universal has its Burt Reynolds's entry, ''Stroker Ace,'' scheduled for July 1. Paramount is waiting until July 15 to release ''Staying Alive,'' directed by Sylvester Stallone, with John Travolta as the same character he played in ''Saturday Night Fever.'' 'Harware' Dominates June

Another tactic that Paramount is using is to place its Dan Aykroyd and Eddie Murphy comedy, ''Trading Places,'' toe-to-toe against the ''hardware'' movies that dominate June -those space and actionadventure films with an accent on technology. ''We're opening 'Trading Places,' which was directed by John Landis, who made 'Animal House,' on June 10,'' said Paramount's motion-picture division president, Frank Mancuso. ''We are positioning it as the comedy of the early summer.''

The success of Paramount's ''Friday the 13th 3-D'' last summer made it obvious that several major studios would be launching 3-D movies this summer. In addition to Columbia's ''Spacehunter,'' Universal has ''Jaws 3-D'' and Paramount has a 3-D comedy about an invisibility potion, ''The Man Who Wasn't There.'' Columbia has taken out doublepage advertisements promising ''incredible firsts'' and ''state-ofthe-art process'' from ''Spacehunter.'' But executives at other studios are afraid audiences will spurn the later 3-D movies if ''Spacehunter'' doesn't deliver what it has promised.

According to Richard Kahn, an M-G-M/U.A. marketing vice president, ''Two kinds of movies have an easy time, at least for the first week: series or sequels and movies with a major star. Nine out of 10 moviegoers will be aware of 'Superman,' 'Jedi' and 'Octopussy' before they open. Because of their stars, 'Stoker Ace' and 'Trading Places' will also have an immediate lock onto an audience.'' Longest Playing Time

Those high-visibility movies will all be in theaters by mid-July. If a studio feels a movie has a good chance of being a major hit, it releases it early in the summer to give it the longest playing time possible. In Mr. Mancusco's words, ''Competition lessens as summer lengthens.'' So August will bring a dozen or more movies with little or no built-in box-office magic. They include Orion's ''Easy Money,'' starring Rodney Dangerfield; Universal's ''Smokey and the Bandit III,'' without Burt Reynolds; M-G-M/ U.A.'s ''Curse of the Pink Panther,'' without Peter Sellers, and Warner Bros.'s ''Risky Business,'' starring an unknown, Tom Cruz.

One or more of the August movies is likely to be an unexpected success, as ''An Officer and a Gentleman'' was last year. And one or more of the eagerly awaited big movies may turn out to be a boxoffice bomb.

Many executives and exhibitors are concerned about the box-office potential of ''Krull,'' Columbia's high-budget sword-and-sorcery movie set in outer space, and Warner Bros.'s ''Twilight Zone,'' four short stories tinged with supernatural overtones, one of which was directed by Steven Spielberg.

Although marketing executives are inclined to offer one of their own movies first as the summer's ''sleeper,'' everybody's second choice was M-G-M/U.A.'s ''WarGames,'' a cautionary tale about a computer whiz kid who almost causes a nuclear war. And this summer's premiere director is expected to be John Badham, the director of both ''WarGames'' and ''Blue Thunder.''

Illustrations: photo of Darth Vader photo of Christopher Reeve and Richard Pryor photo of Roger Moore