USMCFLYR

You will get more complete answers soon from those who have worked with and/or flown Predator's, but the type of UAVs that CBP flies don't go up to FL500.

"U.S. Customs and Border Protection was reported in 2013 to be operating 10 Predators and to have requested 14 more.[41][42] "

Here is a link to the Wiki article on the Predator
:https://en.wikipedia.org/wiki/Genera..._MQ-1_Predator

Here is the fact sheet with some stats:
Performance
Maximum speed: 117 kn (135 mph, 217 km/h)
Cruise speed: 70 kn (81 mph, 130 km/h) to 90 kn (100 mph; 170 km/h)
Stall speed: 54 kn (62 mph, 100 km/h)
Range: 675 nmi (777 mi, 1,250 km)
Endurance: 24 hours[1]
Service ceiling: 25,000 ft (7,600 m)

And MQ-9s Predator B:
U.S. Homeland Security​[edit]




U.S. Customs and Border Protection's Predator B





CBP's Predator B




CBP's maritime variant of the Predator B, named "Guardian"




File:CPB UAS Sample Surveillance Video 02282008 .theora.ogv
Play media

A CBP Predator B helps direct border agents towards a migrant group crossing the US-Mexico border, c. February 2008

U.S. Customs and Border Protection (CBP) operated nine MQ-9s in August 2012. Two were based in North Dakota at Grand Forks Air Force Base, four were based in Arizona, at Fort Huachuca and one was based at the Naval Air Station Corpus Christi, Texas.[80] These aircraft were equipped with GA-ASI's Lynx synthetic aperture radar and Raytheon's MTS-B electro-optical infrared sensors.[81] CBP also had two maritime MQ-9s called Guardians, based at Cape Canaveral Air Force Station, Florida and Naval Air Station Corpus Christi, Texas.[82] The Guardians were equipped with the SeaVue marine search radar; their electro-optical infrared sensor was optimized for maritime operations.[80] The CBP operates one MQ-9 Guardian jointly with the U.S. Coast Guard (USCG) out of land-based stations in Florida and Texas.[83]

The United States Department of Homeland Security initially ordered one Predator B for border protection duty, referred to as MQ-9 CBP-101. It began operations 4 October 2005 and crashed in the Arizona desert on 25 April 2006. The US's NTSB determined that the crash's most likely cause was pilot error by the ground-based pilot, inadvertently shutting down the UAV's engine by failing to follow the checklist.[84] During its operational period, the aircraft flew 959 hours on patrol and played a role in 2,309 arrests. It also contributed to the seizure of four vehicles and 8,267 pounds (3,750 kg) of marijuana.[85]

A second Predator B, called "CBP-104" (initially referred to as "CBP-102"), was delivered in September 2006 and commenced limited border protection operations on 18 October 2006. The president's FY2006 emergency supplemental budget request added $45 million for the program and the FY2007 Homeland Security Appropriations Bill added an additional $20 million. In October 2006, GA-ASI announced a $33.9 million contract to supply two more Predator B systems by the fall of 2007.[86] On 16 February 2009, the program was further expanded to include patrols of the Canada–US border.[87]

On 14 October 2013, an MQ-9 began patrolling the Manitoba portion of the U.S.-Canada border. The UAV is based at Grand Forks Air Force Base and will watch the 400 km (250 mi)-long border. The drone will not carry weapons and needs permission to enter Canadian airspace. U.S. authorities fear that drug smugglers, migrants, and terrorists may exploit the long border. The use of the unmanned surveillance aircraft is an enhancement of the partnership between U.S. and Canadian agencies.[88]

In January 2014, Customs and Border Protection grounded its UAVs temporarily after an unmanned aircraft was ditched off the coast of California by the operator due to a mechanical failure on 27 January 2014.[89]