Half the globe is now online: How to connect the other half?

By the end of the year 3.5 billion people, 47 percent of the global population, will have access to the internet, according to a new report from the United Nations International Telecommunications Union.

But internet access is far from evenly distributed. While 80 percent of the population in developed countries uses the internet, only 40 percent has access in developing countries, and less than 15 percent in less-developed countries (LDCs) do, leaving female, elderly, less educated, poorer, and rural populations offline.

"Internet penetration levels in LDCs today have reached the level enjoyed by developed countries in 1998, suggesting that the LDCs are lagging nearly 20 years behind the developed countries," the report said.

To address this problem, Facebook’s Mark Zuckerburg launched internet.org, an initiative to bring internet access and the benefits of connectivity to the entire world. He quickly discovered that spreading internet to impoverished regions comes with a litany of structural, political, and economic challenges.

While internet companies have expanded affordable smartphone and data plan options in wealthy areas, they have less incentive to push into poorer markets. The report blames the high costs associated with extending services and infrastructure to remote areas as one of the reasons non-wealthy areas lag behind.

To bypass infrastructure challenges, Facebook decided to work from above and began testing high-altitude, solar-powered drones, designed to stay aloft for months at a time, that could produce an internet signal for the people below.

While a June test of the drone was considered a success by Facebook, the The National Transportation Safety Board has announced it is conducting an investigation into 'substantial' problems that occurred during the flight.

Facebook is investigating too, according to a blog post. “We are still analyzing the results of the extended test, including a structural failure we experienced just before landing,” wrote the team.

This is only the latest in a number of setbacks Facebook has encountered while trying to connect the entire world.

A satellite that would have beamed internet down over Africa was destroyed in September in when the SpaceX rocket meant to lift the satellite into orbit exploded before liftoff.

There has also been political pushback to Facebook’s initiative, particularly in India, where locals see it not as a charitable project, but as a land-grab of the Indian internet market, Bloomberg reports.

But Facebook does not seem discouraged. The company's a statement on the investigation emphasized the positive outcomes of the test flight, and at an Asia-Pacific Economic Cooperation summit in Peru, Zuckerberg reiterated his commitment to global internet access.

"If we make the right investments now, we can connect billions of people in the next decade and lead the way for our generation to do great things," Zuckerberg said in a Facebook post from the summit on Saturday.

Material from Reuters contributed to this report.