Yes, it is.

You obviously know that at home you get a certain voltage (e.g. 220V), and on your laptop charger it says that it accepts only that specific voltage. But in reality there is a certain level of fluctuation even at your house and unless you are using a cheap quality charger, the charger itself is designed with this in mind. Plus, no airline would go that far as to add plug to all their seats and install an additional electricity transformer, just to fry all passenger devices once in a while.

S*it can always happen, obviously, but it can happen at home exactly like it can happen in flight.

Yes, it is safe.

You obviously know that at home you get a certain voltage (e.g. 220V), and on your laptop charger it says that it accepts only that specific voltage, so when you use your laptop at home you feel safe. But in reality there is a certain level of fluctuation even at your house and unless you are using a cheap quality charger, the charger itself is designed with this in mind. Plus, no airline would go that far as to add plug to all their seats and install an additional electricity transformer, just to fry all passenger devices once in a while.

S*it can always happen, obviously, but it can happen at home exactly like it can happen in flight.