What to do after a claim for compensation is rejected

Under EC261, there are two different things an airline may owe you:

• Care and assistance. This is something that they can't get out of unless there are really very, very special circumstances (think a volcano erupts). This includes meals, hotels (and associated transfers) if there's an overnight stay, communication... They should have provided an hotel room for you in this situation. However, it's unclear what recourse you have if you didn't get it at the time (if you paid for a hotel, they have to reimburse you, within limits, but if you didn't...).

• Compensation for delays. Here, you were very clearly delayed enough at your final destination (that's all that counts) to qualify for compensation (a few hundred euros, the exact amount depends on the distance between origin and destination airports), unless there are extraordinary circumstances. Cabin crew being sick are not extraordinary circumstances. Strikes by airlines personnel aren't either. Surprise strikes of third parties may be extraordinary circumstances, as well as strikes by ATC personnel. Strikes of third parties known in advance aren't. So you would need to ascertain what exactly happened, as they seem to present a different story.

However, as you had a connection, and there were issues on both flights, it will be difficult to determine which of the issues are considered the cause of the final delay: the initial delay on the first flight, or the cancellation of the second one. This can be quite tricky to resolve.

Many (most?) airlines will try to get out of EC261 compensation through any means (we have had some sordid examples around here). Sadly, the way to get compensation (if you are indeed owed compensation) once they refuse your initial request is quite complex. In some cases there may be a designated Alternative Dispute Resolution (ADR) party designated by the airline, which may help streamline the process. Otherwise, you will have to complain to the relevant national authority, which usually has very little teeth, or through the courts, which will take time and money (as you should hire a lawyer if you want to have any chance against the airline).

It would help if you could determine what the exact circumstances were (for both flights). News reports about a strike (or the absence thereof), records of departures/arrivals at the same airports, etc. would help. If you are convinced your case has merit, then you can go ahead, otherwise it's probably a waste of time. One simple solution is to use the services of one of the many companies that will fight this for you in exchange for a commission (usually around 30% of the compensation). They have a lot of experience with this and will be able to tell you if the case has any chance to be won. The other solutions are usually more complex.

Regarding your list of complaints:

1- The delay of the flight more than 09 hours.

2- Cancellation of the second flight.

These two are one and the same, really. For EC261 compensation, the only thing that counts is how late you were at the final destination.

3- The time spent at the two airports without food and medicines.

4- The night I spent at the airport.

See above about food and hotel. They were definitely in breach of their obligations here. What kind of compensation you can get is unclear.

Not having your medicines will not be considered by anyone. It is your own responsibility to have the required medicines and take into account possible delays. You should never, ever have required medicines in your checked luggage if you may need them within 48 hours. Flight delays and cancellations do happen for many reasons, luggage gets delayed, misrouted or lost every day. You can't blame the airline (or anyone, really) if you don't have required medication for at least 48 hours at hand at all times.

5- The important meeting that I missed.

6- The incident that was happened to my checked luggage.

EC261 does not provide for those. You may want to examine compensation under the Montreal Convention. Usually this is much, much less useful than EC261, but you never know. I'm quite surprised by the fact he airline didn't deliver directly to your home/hotel/work.