Analysis of Flight Aware HAR FILE

I am learning software testing and currently working on an analysis of a Flight Aware HAR file. After downloading the HAR file, I extracted some data using the jq tool. Now, I want to perform further analysis on the extracted data and have a few questions.

For example, I understand that the IATA code is a three-letter code, but why is a four-letter code assigned to the ‘IATA’ field in the JSON file, instead of the ICAO code field?
“properties”: {
“label”: “AK45”,
“ops”: 0.0,
“wx”: “”,
“code”: “AK45”,
“icao”: “”,
“iata”: “AK45”,
“altIdent”: null,
“isAirport”: true,
“isHeliport”: false,
“isCustomGlobal”: null

Also, could you clarify what ‘prominence’ refers to in this context? Is the negative value correct?
Altitude is also a negative number.
“properties”: {
“flight_id”: “UAL65-1737612249-airline-1447p:0”,
“prefix”: “UAL”,
“direction”: 206,
“type”: “B78X”,
“ident”: “UAL65”,
“icon”: “heavy_2e”,
“ga”: false,
“landingTimes”: {
“estimated”: “1737828660”
},
“origin”: {
“icao”: “LPPT”,
“iata”: “LIS”,
“isUSAirport”: false
},
“destination”: {
“icao”: “KEWR”,
“iata”: “EWR”,
“TZ”: “:America/New_York”,
“isUSAirport”: true
},
“prominence”: -548,
“flightType”: “airline”,
“projected”: 0,
“altitude”: -2,
“altitudeChange”: “D”,
“groundspeed”: 95
}

AK45 is the FAA identifier for the private Grebe Lake Airport at Wasilla, AK.

IATA codes can be 1, 2, 3, or 4 characters depending on their use.
For example
Class codes = 1 character
Airline codes = 2 characters
Country codes = 2 characters
Tax codes = 2 characters
Aircraft type = 3 characters
Airport codes = 3 characters
Region codes = 3 characters
Meal codes = 4 characters

In this case IATA is referring to IATA airport code, which is a three-letter code designating airports. I want to know why a four-letter code is assigned to IATA field?

Most likely there was no other place to put the FAA LID airport code. That airport does not have an IATA code assigned. IATA codes do not contain numbers so there is no chance of misidentifying the code as an IATA airport. Why don’t you ask Flight Aware, it’s their file?