Lockheed EP-3

The Lockheed EP-3 is electronic signals reconnaissance version of the P-3 Orion, operated by the United States Navy.
Development.
A total of 12 P-3C aircraft were converted to replace older versions of the aircraft, which had been converted in the late 1960s and early 1970s. The aircraft is known by the acronym ARIES, or "Airborne Reconnaissance Integrated Electronic System". and has Signals intelligence (SIGINT) capabilities. SIGINT is the interception of signals, whether communications between people (communications intelligence—abbreviated to COMINT) or from electronic signals not directly used in communication (electronic intelligence—abbreviated to ELINT). The EP-3E generally has a crew of 24, including linguists, cryptographers and technicians.
The squadrons that flew the EP-3E also flew the Lockheed EC-121 Warning Star from 1962 to 1974 and the Douglas EA-3B Skywarrior from 1960 to 1991. There are 11 EP-3Es in the Navy's inventory, the last of which was delivered in 1997.
Hainan Island incident.
On April 1, 2001 an aerial collision between a United States Navy EP-3E ARIES II, a signals reconnaissance version and a People's Liberation Army Navy Shenyang J-8II fighter resulted in an international incident between the United States and China. Operating about 70 miles (110 km) away from the PRC island province of Hainan Island, the EP-3 was intercepted by two J-8II fighters. One of the J-8IIs collided with it. The J-8II crashed into the sea and the pilot, Lt. Cdr. Wang, was seen to eject after the collision. His body was never recovered and he was declared dead. The EP-3 came close to becoming uncontrollable, at one point sustaining a nearly inverted roll, but was able to make a successful, unauthorized emergency landing at Lingshui airfield on Hainan island, where the two J-8II fighters involved in the incident had been based. At least 15 distress signals from the Orion had gone unanswered. The crew and the plane were subsequently detained by Chinese authorities, accused of "killing the Chinese pilot".
After several days of interrogations, the crew was repatriated separately to the United States while the aircraft remained in China, reportedly taken apart for research on American intelligence technology. Although the crew attempted to destroy as much classified material, hardware, and software on the aircraft prior to the emergency landing, there is little doubt that the EP-3 was exploited by Chinese intelligence services. An American team was later permitted to enter Hainan in order to dismantle the aircraft, which was subsequently airlifted on board two of Russia's Polet Airlines Antonov An-124 Ruslan back to the United States for reassembly and repair.
Other incidents.
On January 29, 2018 a near accident was reported on the Black Sea, when a Russian Su-27 passed a US EP-3 at a distance of several feet.
In a separate incident, on the 5th of November 2018, a US EP-3 was again claimed to have been closely passed in international airspace by a Russian Su-27. 
On July 19, 2019, a U.S. EP-3 was "performing a multi-nationally recognized and approved mission in international airspace" over the Caribbean Sea, when a Venezuelan Su-30 aggressively shadowed it at an unsafe distance. 
EP-X.
Boeing has started working on an unscheduled replacement aircraft, the EP-X, based on their 737.
On 16 August 2009, The Navy issued an "EP-X Analysis of Alternatives" that called for "information useful for the execution of the Electronic Patrol-X (EP-X) program which will recapitalize the EP-3E aircraft to provide tactical, theater, and national level Intelligence, Surveillance, Reconnaissance, and Targeting (ISR&T) support to Carrier Strike Groups and to Theater, Combatant, and National Commanders."
On 23 September 2009, leaked Navy budget documents for FY2011 revealed that the EP-X program would be delayed rather than started in that year.
On 1 February 2010, President Obama unveiled his proposed budget for 2010. This budget called for, among other things, canceling the EP-X program.
Replacement.
After the cancellation of the EP-X Program, the US Navy has planned to replace the EP-3E Aries II with the MQ-4C Broad Area Maritime Surveillance (BAMS) unmanned aircraft and the MQ-8B Fire Scout unmanned helicopter. All P-3 Orion aircraft assigned to special projects squadrons (VPU) and all EP-3E Aries II aircraft are expected to fully retire by 2025.