When your beloved pet bird finds out it can fly, there is very little you can do to stop it.  There are however a few things you can do to try and recover your pet bird.

The problem is not letting the bird free, the problem is that this bird has no idea how to survive on its own and it is therefore imperative that you do your best to find it and return the bird to the safety of your home.

How to Proceed

1. Act Immediately - Locating your bird is the first step. It is critical that this is done as quickly as possible. So, start searching as soon as you realize your bird is lost.
2. Place his/her Cage Outside - Put the cage outside and fill it with his/her favourite treats and freshwater. Leave the cage door open.
3. Canvas the Neighbourhood - Most birds are recovered within 3 kilometers of the escape location, so within hours you need to have everyone within that area know how to contact you. Let your neighbours know that you lost your bird. Walk around the neighbourhood and call his/her name. The best way to do this is to literally go door to door to every home within a half a mile of the escape location.
4. Disburse Fliers - Post and pass out fliers with a detailed description of your bird and a picture if you have one. Include instructions that say to leave the bird alone and not attempt to recover it and your contact phone.
5. Ensure that as many eyes and ears as possible are on the lookout - Give fliers to school crossing guards and distribute them to students exiting schools local to the escape location.
6. Keep Y our Phone Charged - The phone number listed on the flier should be a fully charged cell phone with service available in the area of loss. If this is not available the phone should be a friend or family member who will be able to contact you while you are out searching.
7. Offer a Reward - Offer a reward for the safe return of your lost bird.

What to Expect

Even brightly coloured parrots blend in amazingly well and are hard to spot. The bird will most likely start calling within the first 24 hours; those close should know how to contact you.
Days are not counted with 24 hours, but how many nights the parrot has been out.

Day 1 is the day of escape whether morning or late in the afternoon.
Day 2 is the day after the first night spent out.
Day 3 is the day after the 2nd night out.
First 24 hours
Looking for parrots should begin the moment they escape and continue until dusk and resume every morning at dawn. Large parrots are quiet and roost at night making searching at night fairly pointless.
Next 24 Hours
If you have not spotted your parrot within the first 24 hours make sure someone does rounds at local shelters and veterinary hospitals on a daily basis. As time passes the chances of recovery lessens so move fast and keep moving. Send your flier to your local avian vet.
Call your local animal care and control and humane society and list your bird missing; Go there every day to see if your bird has been surrendered.
Day Three
By day 3 you should enlarge your flier area to 1 mile and grow it each day thereafter. This is the most critical part of recovery. DON'T GIVE UP TOO SOON!

Place an ad in your local newspapers. Some of them place ads about lost and found animals for free.
Seek a bird rescue organization near you and let them know you lost your bird. They often take in stray birds as well.
List your bird as missing at other lost and found bird websites:

Recovering a Large Parrot
Birds instinctively tend to fly when their adrenalin level is high. They also generally fly up to the highest point they can land. However, most pet birds today have never fully fledged (fledging is the process of learning how to fly). While smaller birds can often fly quite easily, larger parrots require more skill to be able to take off and land at will, and navigate where they want to go.

Wait Until the Bird is Ready to Come Down
Consequently, if a bird flies to something high, like a tree, it may not have the skill and experience to know how to fly down. This means that most large parrots who escape their caregivers need to be found quickly and then monitored until they are ready to climb down on their own. Once the parrot is located, if it is above arms reach, you need to wait until the parrot climbs down willingly. The parrot will do this on its timetable, not yours. Food treats and attention by the caregiver are the only tools that should be used to encourage the parrot to come down sooner, rather then later.

Do NOT Spook the Bird into Taking Off Again
Chances are, the parrot will not come down until s/he has spent two nights out. Thus, your goal is to ensure that nothing spooks the parrot into flight. The worst thing that can happen is for the parrot to take flight again so you have to resume your search. This means that under no circumstances should anyone climb a tree, use a ladder, net, pole, hose, or other reaching item to access the parrot. A few cold nights are far less dangerous to the bird than having it fly onto a power line or to a location where you can't spot it. The hard part is finding a bird!

Observe the Bird
The parrot should be observed from dawn to dusk. The parrot will probably just roost. Food should not be left out or distributed around location. The goal is for the parrot to climb down to the caregiver. This usually happens on day three. Avoid too many strangers at the location. You want the parrot to focus on its caregiver.

Watch for signs the parrots is ready to climb down:
Fluttering of wings
Movement in the tree to ensure a good view of caregiver
Calls to caregiver when not in view
The movement toward the caregiver

Start the Food Fest
Once the parrot is showing clear signs of being ready to climb down, start passing favorite foods to other spotters around the location in view of parrot. Make yummy sounds showing great pleasure in having such wonderful treats. Use fairly large visible portions of brightly or strong smelling foods that the parrot sees as a treat. This should get the parrot fairly excited if it is ready to come down. Continue with the food fest with only the primary caregiver directly at the base where the parrot will need to climb down.

Leave and Return
If the parrot settles a bit during day three, leave a spotter at the location and have the primary caregiver leave for an hour or so, returning with a plate of food. Offer the food to the spotter and start the food fest over again. Most likely, by the end of day three, the parrot will give in and climb down to its caregiver.
If it is getting late in the day on day 3 and the parrot is looking like it is settling in for the night, call the pizza delivery guy for one last shot for that day.
By day 4 most parrots will climb down to anyone, but for those few holdouts, just continue as on previous days. The parrot will eventually climb down when it is ready.

Be Prepared for an Escape
For all pet owners, please have fliers ready just in case. Take 30 minutes now to make one up for each pet. Have copies available so a friend can make copies for you while you do an initial search.
You don't want to take this time after the escape nor do you want to find you have no photo. A photo should show the bird in full colour both back and front view and with wings spread if possible. If you leave town and your parrots in the care of others, make sure they fully understand the recovery process and that they understand to notify you immediately if your bird escapes.

Source: Brainy Birds Training & Rescue Facility

NOTE:  Pet Healthcare does not agree that birds be kept as pets.  Their wings should never be clipped.  We believe that if you want a bird to be your pet, allow the bird to make that decision for itself.  It is cruel to confine any animal to a life of captivity in a cage.  We acknowledge that you have a wonderful relationship with your pet bird, but we hope that you will think twice before you decide to get another bird caged in for life.