Question: What is the call sign of the airline that operates the flight with United Express Flight 3411 incident?

Context:
Republic Airline
Republic Airline Inc., operating as Republic Airline, is a regional airline subsidiary of Republic Airways Holdings that operates service as American Eagle, Delta Connection, and United Express using a fleet of Embraer 170 and Embraer 175 regional jets.
 It is headquartered in Indianapolis, Indiana.
 Its call sign "Brickyard" is derived from the nickname of the Indianapolis Motor Speedway.
United Express Flight 3411 incident
On April 9, 2017, O'Hare International Airport police violently and forcibly ejected passenger David Dao from United Express Flight 3411 after he refused to depart the airplane upon the demand of management.
 Dao screamed as officers pulled him out of his seat, and his face hit an armrest during the struggle.
 Officers then dragged him, apparently unconscious, by his arms on his back along the aircraft aisle past rows of onlooking passengers.
 He was later seen with blood around his mouth.
 Prior to the confrontation, managers offered travel vouchers to passengers to vacate their seats to make room for four airline employees who needed to travel to the destination, Louisville International Airport, but none of the fliers accepted.
 Four passengers were then selected for involuntary removal from the flight.
 Three other passengers complied, and Dao was selected to be fourth.
 Republic Airline operated the scheduled passenger flight on behalf of United Express, a United Airlines regional branch.
United Express Flight 6291
United Express Flight 6291 was a regularly scheduled United Express flight from Washington D.C. to Columbus, Ohio.
 It was a service operated by Atlantic Coast Airlines on behalf of United Express.
United Express Flight 2415
United Express Flight 2415 was a regularly scheduled flight from Seattle to Pasco, Washington, operated using a BAe Jetstream 31.
 On December 26, 1989, Flight 2415 crashed while attempting to land at Pasco's Tri-Cities Airport, killing both pilots and all four passengers aboard.
Air Japan
Air Japan Co., Ltd. (株式会社エアージャパン , Kabushiki-gaisha Eā Japan ) is a charter airline based on the grounds of Narita International Airport in Narita, Chiba in Japan.
 It operates scheduled services under the ANA brand.
 It should not be confused with Air Nippon, another ANA subsidiary, or Japan Airlines (JAL), ANA's competitor.
 Its main base is Narita Airport.
 It was announced on 2 April 2010 that Air Japan and ANA & JP Express will merge, with Air Japan being the surviving company.
 Air Japan uses the All Nippon call sign on all flights except the Seoul Incheon and Narita-Honolulu routes which use the Air Japan call sign.
Aviator call sign
An aviator call sign or aviator callsign is a call sign given to a military pilot, flight officer, and even some enlisted aviators.
 The call sign is a specialized form of nickname that is used as a substitute for the aviator's given name.
 It is used on flight suit and flight jacket name tags, painted/displayed beneath the officer's or enlisted aircrewman's name on aircraft fuselages or canopy rails, and in radio conversations.
 They are most commonly used in tactical jet aircraft communities (i.e., fighter and attack) than in other aircraft communities (i.e., airlift, mobility, maritime patrol), but their use is not totally exclusive to the former.
 Many NASA Astronauts with military aviator backgrounds are referred to during spaceflights by their call signs rather than their first names.
Le Conquet radio
Le Conquet radio or Call sign FFU (station "Française Fixe de Ushant") was a French maritime radio station located on of City Le Conquet (La Pointe du Renard 4°43'58"W 48°20'24"N).
 The station was established in 1952, by the French Administration of France Télécom, as a result of the work by Call sign Ushant TSF, Call sign FFU.
Provincetown-Boston Airlines
Provincetown-Boston Airlines (IATA: PT, ICAO: PBA, Call sign: PBA) was an airline that operated between 1949 and 1989.
 The airline operated a route network in New England, New York, Pennsylvania, and Florida, and at one time was the largest commuter airline in the United States before its purchase by People Express Airlines and then eventual consolidation with other commuter airlines into Continental Express, now United Express after its merger.
United Express Flight 5925
United Express Flight 5925, operated by Great Lakes Airlines with a Beechcraft 1900 twin turboprop, was a regularly scheduled flight from Chicago O'Hare International Airport to Quincy, Illinois, with an intermediate stop in Burlington, Iowa.
Air Wisconsin
Air Wisconsin Airlines is a regional airline based at Appleton International Airport in the town of Greenville, Wisconsin, United States, near Appleton.
 Air Wisconsin is the largest privately held regional airline in the United States.
 It currently operates regional jet flights as American Eagle under contract to American Airlines via a code sharing agreement, serving cities in the U.S. and Canada with hubs at Boston Logan International Airport (BOS), Charlotte Douglas International Airport (CLT), Philadelphia International Airport (PHL) and Ronald Reagan Washington National Airport (DCA) .
 Air Wisconsin previously operated United Express service on behalf of United Airlines followed by US Airways Express service on behalf of US Airways prior to becoming an American Eagle regional air carrier.
 The company has announced it will once again partner with United Airlines as a United Express code sharing air carrier with primary hubs to be located at Chicago O'Hare International Airport (ORD) and Washington Dulles International Airport (IAD) beginning in September 2017 and will be "exclusively operating" as United Express by March 2018.

Answer: Brickyard