The DARPA program is called Airborne Launch Assist Space Access, aka ALASA. It's been around for a few years, but the news here is that Boeing has been selected to build an operational prototype launch system. The idea is that using an aircraft like this will substantially increase the affordability and versatility of space access for small payloads, reducing launch costs to something around $1 million for a 100 pound payload to low Earth orbit. This sounds like a lot to those of us who wish we had $1 million, but for governments and research institutions, that's couch-cushion money.
Boeing is supposed to design the system and conduct test launches within the next 11 months, and we can only hope that it looks as cool as these concept images.