You can sort objects using queries arguments such as those found in the list method:

def airports = Airport.list(sort:'name')

However, you can also declare the sort order declaratively:

class Airport {
	…
	static mapping = {
		sort "name"
	}
}

You can also configure the sort order if necessary:

class Airport {
	…
	static mapping = {
		sort name:"desc"
	}
}

Alternatively, you can configure sort order at the association level:

class Airport {
	…
	static hasMany = [flights:Flight]
	static mapping = {
		flights sort:'number'
	}
}