The plane left Philadelphia's Northeast Airport around 9:30 p.m. Thursday.
According to Police spokeswoman Corinne Geller, the two men onboard were taking infrared photographs for an aerial photography company.
They were headed to Manassas from Philadelphia, but rerouted to Dulles when they encountered electrical problems and ran low on fuel.
The pilot's attempts to reroute to a local airport failed, and he crashed into an apartment on the 2200 block of Astoria Circle.
Officials say if that plane was full of gas, it could have become a fireball when it struck the apartment with four adults and two children asleep inside.
A next door neighbor described how he felt at the time of impact, saying, "We were sleeping, we heard some noise the building started to shake, after that I heard some banging on the doors and it was my neighbor, he looked in shock as crews tried to figure out how to extract the plane."
The pilot onboard, 61-year-old William Larson, was hospitalized with serious injuries. However, he told Action News' affiliate WJLA, "It's a miracle I'm alive."
The other person onboard is identified as Tache Alejandro. So far, there is no word on his condition.
A woman who was in the apartment was taken to the hospital with non-life-threatening injuries.
The Red Cross is helping nine adults, seven children and pets who had to leave the building.
The FAA has no reports of any injuries on the ground and will continue to investigate.
Information provided by the Associated Press was used in this article.