What Are Alternate Airports?
An alternate airport is a pre-planned diversion destination you can fly to if you cannot land at your intended destination. Reasons for diverting include weather below minimums, runway closure, equipment failure, or other operational issues. Regulatory authorities (ICAO, EASA, FAA) require that most IFR flights carry enough fuel to reach at least one alternate airport.
At JetStream Virtual, the alternate selection is Step 2 of the flight planning process — right after selecting your aircraft and before configuring the flight plan in SimBrief.
How the Alternate Selection Works
Finding Nearby Airports
When you reach the alternate selection page, the system automatically searches for airports near your destination using a geographic radius calculation. Up to 8 candidate airports are returned, sorted by distance. The system considers:
- Distance — airports within approximately 200 nautical miles of your destination
- Runway length — whether the airport has a runway long enough for your aircraft type
- Airline operations — whether JetStream Virtual already operates flights to that airport (shown with a green Airline Operates Here badge)
Decoded Weather Information
For each candidate airport, you'll see decoded METAR data showing:
| Field | Description | Colour Coding |
|---|---|---|
| Wind | Direction (degrees) and speed (knots), including gusts | Orange if gusts ≥ 25kt |
| Visibility | In kilometres or statute miles | Green ≥ 5 km, Orange ≥ 1.5 km, Red < 1.5 km |
| Ceiling | Lowest BKN/OVC cloud layer in feet AGL | Green ≥ 1,000ft, Orange ≥ 500ft, Red < 500ft |
| Temperature | Degrees Celsius | — |
| QNH | Altimeter setting in hPa or inHg | — |
| Wx | Significant weather phenomena (RA, SN, FG, TS, etc.) | — |
Runway Wind Analysis
This is one of the most powerful features. For every runway at the airport, the system calculates:
- Headwind Component
- Shown in green with an upward arrow (▲). A headwind is favourable for landing — it reduces ground speed and shortens landing distance.
- Tailwind Component
- Shown in red with a downward arrow (▼). A tailwind increases landing distance and is generally undesirable. Most aircraft have a maximum tailwind component of 10–15 knots.
- Crosswind Component
- Shown with L (left) or R (right) indicator. Colour-coded: green ≤ 10kt, orange ≤ 20kt, red > 20kt. Maximum demonstrated crosswind limits vary by aircraft type.
The best runway is automatically highlighted with a green ⭐ star — this is the runway with the highest headwind component (most favorable landing conditions).
How to Read Wind Components
The wind component calculation uses trigonometry based on the angle between the wind direction and the runway heading:
- Headwind = Wind Speed × cos(Wind Direction − Runway Heading)
- Crosswind = Wind Speed × |sin(Wind Direction − Runway Heading)|
For example, with wind 270°/15kt and runway 24 (heading 240°): the angle difference is 30°, giving a headwind of 13kt and a crosswind of 8kt — excellent conditions.
Selecting Your Alternates
You can select 1 to 4 alternate airports by clicking on their cards. Selected airports are highlighted in green with a checkmark. Consider:
- Pick airports with good weather — especially if your destination weather is marginal
- Prefer airports where the airline already operates (logistics and ground support are available)
- Consider runway suitability for your aircraft type
- Diversifying: pick alternates in different directions from your destination in case of widespread bad weather
Auto Planning
If you prefer, click Auto Planning to let SimBrief automatically select the best alternate based on distance, weather, and runway availability. This is a good option if you're unsure.
What Happens Next
Your selected alternates are sent to SimBrief when generating the OFP. SimBrief will:
- Calculate alternate fuel — the fuel required to fly from destination to the alternate
- Include the alternate in the ATC flight plan
- Add alternate airport weather to the briefing package
- Show the alternate route and fuel burn in the OFP
Raw METAR/TAF Data
You can always view the raw (undecoded) METAR and TAF by clicking the "Raw METAR/TAF" toggle at the bottom of each airport card. This shows the original aviation weather report as issued by the meteorological office.