Error when Search() Action Method returns Index View() - asp.net

Question

I have a Search Form which goes to my Search() action method within my Home Controller. and returns View("Index")
Search() method:
public IActionResult Search(SearchQuery FormData)
{
List<Flight> flights = new List<Flight>();
flights = (from flight in _context.Flights
where flight.FlightDateTime.Date == FormData.PreferredFlightTime.Date
&& flight.ArrivalAirportId == FormData.ArrivalAirportId
&& flight.DepartureAirportId == FormData.DepartureAirportId
select flight).ToList();
ViewBag.FlightSearchResults = flights;
return View("Index");
}
Upon the initial load of the homepage it works fine when loading my Index() method and returning the view.
public IActionResult Index()
{
HomeViewModel mymodel = new HomeViewModel();
mymodel.Airports = GetAirports();
return View(mymodel);
}
However once the search form is submitted and the Search() action method is called, when the method returns return View("Index"); the page will not load due System.NullReferenceException: 'Object reference not set to an instance of an object.'
The above exception is thrown when it reaches #foreach (Airport airport in Model.Airports)
Search form:
#using FlightBooker;
#model FlightBooker.Models.HomeViewModel;
<form asp-controller="Home" asp-action="Search" method="post">
<div class="form-group">
<label for="fromAirport">Flying from:</label>
<select name=" {DepartureAirportId" class="form-control">
#foreach (Airport airport in Model.Airports)
{
<option value="#airport.AirportId">#airport.AirportCode</option>
}
</select>
<div class="form-group">
<label for="toAirport">Flying to:</label>
<select name="ArrivalAirportId" class="form-control">
#foreach (Airport airport in Model.Airports)
{
<option value="#airport.AirportId">#airport.AirportCode</option>
}
</select>
</div>
<label for="fromAirport">Departure Date:</label>
<br />
<input type="date" / id="date" name="PreferredFlightTime">
<br />
<label for="fromAirport">No. passengers:</label>
<select class="form-control" name="TotalPassengers">
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
</select>
<button type="submit" class="btn btn-primary mt-3">Search Flights</button>
</div>
</form>

Answer 1

Comment from Codecaster above solved this. I updated my Search() action method passing the model to the Index view and repeating the code in my index method.
Updated Search() action method:
public IActionResult Search(SearchQuery FormData)
{
List<Flight> flights = new List<Flight>();
flights = (from flight in _context.Flights
where flight.FlightDateTime.Date == FormData.PreferredFlightTime.Date
&& flight.ArrivalAirportId == FormData.ArrivalAirportId
&& flight.DepartureAirportId == FormData.DepartureAirportId
select flight).ToList();
ViewBag.FlightSearchResults = flights;
HomeViewModel mymodel = new HomeViewModel();
mymodel.Airports = GetAirports();
return View("Index", mymodel);
}