Divide a MongoDB document into multiple documents based on Date Field using aggregation

I have a document on MongoDB that contains flight data records. This data goes back 4 years , and is mixed up in the flight_records array shown in the sample below. I want to split this document into separate documents based on the Year of the record. My Sample Document is as follows -

{
"flight_number": "AS6312",
"airlines_code": "AS",
"flight_records": [{
"status": "Landed 13:35",
"origin": "ONT",
"destination": "SEA",
"date_of_journey": "2023-12-21",
"scheduled": {
"dep": 1671648300,
"arr": 1671658500
},
"real": {
"dep": 1671649420,
"arr": 1671658520
}
},
{
"status": "Canceled",
"origin": "ONT",
"destination": "SEA",
"date_of_journey": "2022-12-20",
"scheduled": {
"dep": 1671561900,
"arr": 1671572100
},
"real": {
"dep": 0,
"arr": 0
}
},
{
"status": "Landed 13:09",
"origin": "ONT",
"destination": "SEA",
"date_of_journey": "2021-12-19",
"scheduled": {
"dep": 1671475500,
"arr": 1671485700
},
"real": {
"dep": 1671475903,
"arr": 1671484184
}
}
]

}

And the expected output is three documents, each for 2021-2023.
The Expected output Document 1 ->

{
"flight_number": "AS6312",
"airlines_code": "AS",
"flight_records": [
{
"status": "Landed 13:35",
"origin": "ONT",
"destination": "SEA",
"date_of_journey": "2023-12-21",
"scheduled": {
"dep": 1671648300,
"arr": 1671658500
},
"real": {
"dep": 1671649420,
"arr": 1671658520
}
}]

}

Similarly , Expected output Document 2-> and so on...

{
"flight_number": "AS6312",
"airlines_code": "AS",
"flight_records": [
{
"status": "Canceled",
"origin": "ONT",
"destination": "SEA",
"date_of_journey": "2022-12-20",
"scheduled": {
"dep": 1671561900,
"arr": 1671572100
},
"real": {
"dep": 0,
"arr": 0
}
}]}

Each of these documents will be saved into separate collections later based on the year of the record. I tried using the $match and the $find but couldn't get the correct output.

Here is the solution that I improvised, I hope others will find it useful.

db.collection.aggregate(
{
"$unwind": "$flight_records"}, 
{
"$group": {
_id: {
$year: {
$toDate: "$flight_records.date_of_journey"
}
},
recordsForYear: {
$push: "$flight_records"
}
}})

And here is the result :

{
"_id": 2021,
"recordsForYear": [
{
"date_of_journey": "2021-11-18",
"destination": "DTW",
"origin": "DCA",
"real": {
"arr": 1.668740944e+09,
"dep": 1.668736446e+09
},
"scheduled": {
"arr": 1.66874124e+09,
"dep": 1.66873524e+09
},
"status": "Landed 22:09"
},
{
"date_of_journey": "2021-11-16",
"destination": "DCA",
"origin": "DTW",
"real": {
"arr": 1.668644421e+09,
"dep": 1.668640813e+09
},
"scheduled": {
"arr": 1.66864524e+09,
"dep": 1.6686396e+09
},
"status": "Landed 19:20"
},
{
"date_of_journey": "2021-11-14",
"destination": "DCA",
"origin": "DTW",
"real": {
"arr": 1.668471887e+09,
"dep": 1.66846811e+09
},
"scheduled": {
"arr": 1.66847244e+09,
"dep": 1.6684668e+09
},
"status": "Landed 19:24"
}
]},{
"_id": 2023,
"recordsForYear": [
{
"date_of_journey": "2023-11-17",
"destination": "DTW",
"origin": "DCA",
"real": {
"arr": 1.668653594e+09,
"dep": 1.668649558e+09
},
"scheduled": {
"arr": 1.66865484e+09,
"dep": 1.66864884e+09
},
"status": "Landed 21:53"
},
{
"date_of_journey": "2023-11-15",
"destination": "DCA",
"origin": "DTW",
"real": {
"arr": 1.668557859e+09,
"dep": 1.668553656e+09
},
"scheduled": {
"arr": 1.66855884e+09,
"dep": 1.6685532e+09
},
"status": "Landed 19:17"
},
{
"date_of_journey": "2023-11-14",
"destination": "DTW",
"origin": "DCA",
"real": {
"arr": 1.668395275e+09,
"dep": 1.668391115e+09
},
"scheduled": {
"arr": 1.66839564e+09,
"dep": 1.66838964e+09
},
"status": "Landed 22:07"
}
]},{
"_id": 2022,
"recordsForYear": [
{
"date_of_journey": "2022-11-17",
"destination": "DCA",
"origin": "DTW",
"real": {
"arr": 1.668730907e+09,
"dep": 1.668727074e+09
},
"scheduled": {
"arr": 1.66873164e+09,
"dep": 1.668726e+09
},
"status": "Landed 19:21"
},
{
"date_of_journey": "2022-11-16",
"destination": "DTW",
"origin": "DCA",
"real": {
"arr": 1.668568424e+09,
"dep": 1.668564614e+09
},
"scheduled": {
"arr": 1.66856844e+09,
"dep": 1.66856244e+09
},
"status": "Landed 22:13"
},
{
"date_of_journey": "2022-11-15",
"destination": "DTW",
"origin": "DCA",
"real": {
"arr": 1.668481169e+09,
"dep": 1.668477413e+09
},
"scheduled": {
"arr": 1.66848204e+09,
"dep": 1.66847604e+09
},
"status": "Landed 21:59"
}
]

}
]