Here are the results. I believe that the delay reasons ZY and ZO mean "late inbound flight" and "operational reasons" respectively.
Results from https://www.ExpertFlyer.com
Code:
Flight Status Search:
Departing on 05/24/18
Flying BA flight 792
Flight Status Depart Location Depart Date Reliability Arrive Location Arrive Date
LHR Scheduled: 05/24/18 4:15 PM GOT Scheduled: 05/24/18 7:20 PM
BA 792 Landed Term: 5 Estimated: 05/24/18 5:29 PM 85% / 14m Term: A Estimated: 05/24/18 8:40 PM
Gate: A9 Actual: 05/24/18 5:29 PM Gate: 19B Actual: 05/24/18 8:40 PM
Comments:
"DOBA792/24MAY
* OPERATIONAL FLIGHT INFO * BA 792 0 TH 24MAY18
CITY INFO HOUR (LOCAL)
LHR ESTIMATED TIME OF DEPARTURE 1720
LEFT THE GATE 1729
TOOK OFF 1804
DELAY ZY
DELAY ZO
ESTIMATED TIME OF ARRIVAL 2041 GOT
GOT AIRCRAFT LANDED 2037
ARRIVED 2040
*1A PLANNED FLIGHT INFO* BA 792 0 TH 24MAY18
APT ARR DY DEP DY CLASS/MEAL EQP GRND EFT TTL
LHR 1615 TH JCDRI/M YB/G 320 2:05
HKMLVNOQSG/G
GOT 1920 TH 2:05
COMMENTS-
1.LHR GOT - MEMBER OF ONEWORLD
2.LHR GOT - DEPARTS TERMINAL 5
3.LHR GOT - 9/ NON-SMOKING
4.LHR GOT - ET/ ELECTRONIC TKT CANDIDATE
5.LHR GOT - CO2/PAX* 117.05 KG ECO, 117.05 KG PRE
(*):SOURCE:ICAO CARBON EMISSIONS CALCULATOR
CONFIGURATION-
320 C 12 M 150