Neil Armstrong was the first man to walk on the moon in 1969 and declared the feat "one giant leap for mankind". Forty-five years later, there are slew of companies wanting to make space travel as regular as airplane trips.

Aerospace market researchers Futron said revenues in the sector could hit $676 million by 2021. In 2012, George Nield, associate administrator for the Federal Aviation Administration's Office of Commercial Space Transportation said space tourism could be a billion-dollar industry in the next 10 years.

Companies including Richard Branson's Virgin Galactic and Elon Musk's SpaceX are among those seeing opportunities in the commercial space market.

Here are some top space travel opportunities that are out of this world.

- By CNBC's Arjun Kharpal

Touted as "the world's first commercial spaceline", Virgin Galactic is offering flights to space for $250,000 a ticket.

The company, owned by Virgin Group boss Richard Branson and Abu Dhabi's Aabar Investments PJS, will take people 50,000 feet up at 3,000 miles per hour in the SpaceShipTwo vehicle. The "astronauts" and then released and able to float in space.

Virgin Galactic is hoping the first flights can take off at the end of 2014.

Branson founded Virgin Galactic in 2004 with Mojave Aerospace Ventures. It later teamed up with Scaled Composites, which builds the group's spacecrafts, to form the Spaceship Company to manufacture the SpaceShipTwo and WhiteKnightTwo spacecraft.

For $95,000, space travelers will be able to take a half-hour trip to space and back on XCOR Aerospace's Lynx Mark I spacecraft.

The Mojave, California-based company was founded in 1999 and since its inception has built and flown two manned rocket-powered aircraft. The first came in 2001 with the EZ-Rocket, followed seven years later by the X-Racer.

XCOR is testing a reusable rocket range called Lynx for its ambitions in the space tourism sector, and hopes to begin commercial flights in 2016.

Earlier this month, XCOR promised to send the Dutch soccer team to space for free if it won the World Cup.

Armadillo Aerospace prepared for lift off in the space tourism sector, but those aspirations soon came crashing back to earth. The company is now in "hibernation mode", according to its founder.

John Carmack, a video game developer, founded the company, and several reports suggested it took $1 million a year to run. Carmack wanted to build a reusable suborbital rocket that could be used for space tourism.

Armadillo created a spacecraft known as STIG which proved to be its downfall. In its third test flight, the STIG-B rocket crashed after the parachute failed to deploy. This setback led Carmack to wind down the company.

Carmack now works at chief technology operator for Oculus VR, the maker of the Oculus Rift virtual reality headset that Facebook bought for $2 billion earlier this year. But the gaming geek has constantly said that external funding could be enough for Armadillo to take off once again.

Space Adventures appears to be light-years ahead of its rivals, having already sent seven people to the International Space Station (ISS) on private flights. But the space tourism company is now eyeing the possibility of sending people to the moon.

Two people have already signed up for Space Adventures' "lunar mission", which is expected to cost at least $150 million per seat, according to the MIT Technology Review. The company is aiming for the journey to take place in 2017.

In 2001, Space Adventures sent Dennis Tito, a former NASA worker, to the ISS, making him the world's first private space explorer.

British singer Sarah Brightman, known for her performance in Andrew Lloyd Webber's "Phantom of the Opera", is the latest space enthusiast to sign up for the ISS trip. She paid a reported $52 million for a 10-day stay at the ISS.

Google co-founder Sergey Brin could soon follow Brightman, and has paid a deposit to Space Adventures, the company's president Tom Shelley told Reuters last month.

Excalibur Almaz is hoping to take explorers to the moon in a converted Soviet-era spacecraft.

A ticket, complete with six months' training, will cost between a $100 million and $150 million dollars, and Art Dula, founder and chief executive of the U.K.-based company, has signaled that the first flights could take place as early as 2015.

Excalibur Almaz predicts that it can sell 30 seats between 2015 and 2025, even with the hefty price tag.

The company has six Soviet-era space vehicles which it has refurbished and upgraded with modern avionics. It has also bought two Soviet Almaz space stations. Three people will be able to travel to the space station at one time in a reusable rocket, that will then bring them back to earth.

Billionaire Elon Musk, the founder of PayPal, Tesla and now SpaceX, is on a mission to get people to Mars.

Musk has long expressed a desire to create a colony on Mars, and earlier this year, on CNBC, he outlined a time frame for the first people to land on the planet.

"I'm hopeful that the first people could be taken to Mars in 10 to 12 years, I think it's certainly possible for that to occur," he said. "But the thing that matters long-term is to have a self-sustaining city on Mars; to make life multi-planetary."

Currently SpaceX has a $1.6 billion contract with NASA to fly cargo to the International Space Station and is aiming to take up crew.

The company has said that creating a reusable spacecraft to take people to and from space will be "disruptive" and make intergalactic travel a reality.

Forget a getaway to Spain or France - a week in space might be better.

If you can cough up the £500,000 ($856,000) required to get into space, and a further £100,000 for accommodation, you may be able to stay in Orbital Technologies' space hotel for five days.

The hotel will be able to accommodate up to seven guests for a period of between three days and six months, and will orbit 250 miles above the earth.

At the time of its launch in 2011, media reports suggested Orbital Technologies would tailor food to each customer's tastes and prepare it on earth before shipping it to space. Showers would not be allowed but alternative methods of washing would be available, and alcohol would be prohibited in the hotel.

Orbital Technologies is aiming to bring the hotel into service in 2016.

Forget aircraft and spaceships, World View wants to take you into orbit in a balloon.

For $75,000, space explorers can take a trip of around two hours to an altitude of just over 100,000 feet, above 99 percent of the earth's atmosphere, according to the company's website.

"The helium-filled balloon is lighter than air and, like ice floating on water, it literally floats above our planet's atmosphere. Just as ice doesn't fly out of a glass of water, it is impossible for the World View capsule to fly off into space," the company said on its site, looking to reassure potential customers.

Customers are in a capsule and float for about 5 hours before descending as the helium is released from the balloon. The balloon is released from the capsule and a parchute-like device called the "ParaWing" takes over to glide the pod back down to earth. The balloon is then recovered and recycled. The entire journey takes between five and six hours.

World View completed a successful test flight last month and is hoping to get explorers into the sky by 2016.